Glucose-sensitive albumin-binding derivatives

ABSTRACT

This invention relates to glucose-sensitive albumin-binding diboron conjugates. More particularly the invention provides novel diboron compounds, and in particular diboronate or diboroxole compounds, useful as intermediate compounds for the synthesis of diboron conjugates. The diboron compounds are characterized by formula (I), which is: R1-X—R2, and wherein “X” is a mono- to multiatomic linker and where R1 and R2, which may be identical or different, each represents a group of Formula (11a) or (IIb) Also described are diboron conjugates represented by the general Formula (I′), which is: R1′-X′—R2′, in which either the moeities R1′ or R2′ or X′ carry a drug that is covalently attached to the diboron compound.

TECHNICAL FIELD

This invention relates to glucose-sensitive albumin-binding diboronconjugates. More particularly the invention provides novel diboroncompounds, and in particular diboronate or diboroxole compounds, usefulas intermediate compounds for the synthesis of diboron conjugates.

BACKGROUND ART

Boronic acids are known for their capability to bind glucose and othercarbohydrates and polyols via the formation of boronate esters. Thisglucose binding is covalent, but the binding equilibrium is fast andreversible, so the binding appears as a complex formation, withdisplacement constants (Kd) in the millimolar range.

Simple boronic acids have pKa values around 9, but since it is theboronate form that binds glucose the strongest (see FIG. 2), tuning ofboronic acid pKa-values using electron-withdrawing groups can providestronger glucose affinity at physiological pH 7.5. Notably,monoboronates bind glucose with Kd values in the range 10-50 millimolar,which does not match well with the physiological range for glucosefluctuations (usually 1-30 mM in diabetes patients).

Stronger glucose affinity can be secured by using diboronic acids, asextensively researched in pursuit of optical glucose sensors. However,diboronates for use as optical glucose sensors are typically colouredand fluorescent (Hansen, Hoeg-Jensen et al, Sensors and Actuators B 161(2012) 45), and such properties are not always desirable for otherapplications, and in particular for therapeutic use.

Diboronate selectivity for glucose over other polyols is a desirableproperty for in vivo use of the compounds. The bulk of diboronateliterature focus on selectivity towards glucose over fructose, butmillimolar blood concentrations of fructose never happen, not even aftera fructose-rich meal. Blood lactate concentrations, on the other hand,are in the low millimolar values at rest, but can increase to 10-20 mMduring extreme exercise. Diboron compounds with selectivity for glucoseover lactate therefore are advantageous for therapeutic use (Hansen,Hoeg-Jensen et al, Tetrahedron 67 (2011) 1334).

The diboronic acids identified for developing optical glucose sensorstypically lack a conjugation handle, and therefore are not particularlywell suited for attachment to protein and peptide-based drugs.

A number of protein and peptide-based drugs, and in particular insulin,GLP-1, and amylin, are used in treatment of diabetes. However, suchtherapeutics have roughly the same bioactivity at low and as well ashigh glucose blood values, and the use of such drugs can lead to verylow blood glucose values, with a concomitant risk of hypoglycemia, whichis a life-threatening condition.

SUMMARY OF THE INVENTION

While blood glucose lowering drugs are successfully used for thetreatment of diabetes, such drugs are also capable of lowering bloodglucose levels even in situations where the patients do not want glucoselevels to change. This may in particular be the case when blood glucoseis below the normal fasting value of approx. 5 mM glucose. Therefore itwould be advantageous to equip diabetes-related peptide and proteindrugs with a glucose-regulated bioactivity, e.g. a weakerglucose-lowering activity of insulin at low blood glucose values.

According to the present invention certain diboronates and diboroxolesare provided, which diboron compounds bind glucose with Kd values in thelow millimolar range (of approx. 0.2-5 mM), and which compounds havegood selectivity for glucose over lactate. Moreover, the diboroncompounds of the invention contain a conjugation handle, e.g. a carboxygroup, so they may be conjugated to diabetes-related protein andpeptide-based drugs, e.g. via attachment to a (native orsubstituted/introduced) lysine residue or an N-terminal of the proteinor peptide.

Moreover, the diboron compounds of the invention are capable of bindingto human serum albumin (HSA), thus possessing a dual action, as thisbinding also is glucose-sensitive (the HSA-bound fraction of the diboronpeptide is inactive due to blocking of the receptor binding sites on thepeptide). Albumin binding can in general prolong the in vivo half-lifeof peptides and protein-based drugs. The prolonged effect is achieved asthe albumin bound fraction is protected from enzymatic degradation andkidney elimination, and only the free fraction is biological active,thus preventing receptor mediated clearance of the albumin boundfraction.

HSA-binding of fatty acid-conjugated protein and peptide-based drugs isan established method for making the peptide/proteins long-acting invivo. However, the fact that the diboron-conjugated peptides andproteins of the invention, comprising no fatty acids, are capable ofbinding to HSA, and that the binding is sensitive to glucose, has neverbeen reported.

Therefore, in its first aspect, the invention provides novel diboroncompounds represented by the general Formula I, as described herein.

In other aspects the invention provides novel diboron compounds ofFormula Ia, and more particular of Formulas Ia, Ib, Ic, Id, Ie, If, Ig,Ih, and Ii as described herein.

In further aspects the invention relates to the use of the diboroncompounds as intermediates in the manufacture of diboron conjugates ofthe invention.

In yet another aspect, the invention provides novel diboron conjugatesrepresented by the general Formula I′, as described herein.

Other objects of the invention will be apparent to the person skilled inthe art from the following detailed description and examples.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further illustrated by reference to theaccompanying drawing, in which:

FIG. 1 shows an illustration of glucose-sensitive albumin binding;

FIG. 2 shows how glucose is binding boronate, illustrated for thepyranose form;

FIG. 3 shows ¹⁹F-NMR signals from the diboron compound of Example 3 infree form (0.1 mM), and upon treatment with albumin (HSA, 1 mM), or withglucose (50 mM) or with albumin (1 mM)+glucose (50 mM), thusillustrating glucose-sensitive albumin binding;

FIG. 4 shows ¹⁹F-NMR signals from the diboron compound of example 20with and without albumin and glucose like FIG. 3;

FIG. 5 shows ¹⁹F-NMR signals from the diboron compound of example 25 inwith and without albumin and glucose like FIG. 3; and

FIG. 6 shows ¹⁹F-NMR signals from the diboron compound of example 26 inwith and without albumin and glucose like FIG. 3.

DETAILED DISCLOSURE OF THE INVENTION The Diboron Conjugates of theInvention

In one aspect the invention provides diboron conjugates represented bythe general Formula I′

R¹′—X′—R²′,

in which Formula I′,

X′ represents a linker of Formula Ia′:

wherein

represents a covalent bond towards R¹′ or R²′;

D represents a drug substance; and

W′ represents a covalent bond, or a linker selected from the groupconsisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, and—NHCH(COOH)CH₂CH₂(C═O)— (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); or

X′ represents a linker of Formula Ib′:

wherein,

represents a covalent bond towards R¹′ or R²′; and

R³′ represent —(CH₂)_(m′)(C═O)—W′—D, wherein

m′ represents an integer in the range of 1 to 4;

W′ represents a covalent bond or a linker selected from the groupconsisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, and—NHCH(COOH)CH₂CH₂(C═O)— (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and

D represents a drug substance; or

X′ represents a linker of Formula Ic′:

which represents a D- or an L-amino acid form; and

wherein,

represents a covalent bond towards R¹′ or R²′;

n′ represents an integer in the range of 1 to 4;

W′ represents a covalent bond or a linker selected from the groupconsisting of

—NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, and—NHCH(COOH)CH₂CH₂(C═O)— (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and

D represents a drug substance; or

X′ represents a linker of Formula Id′:

which represents a R,R or S,S, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine;

wherein,

represents a covalent bond towards R¹′ or R²′;

R⁴′ represents —(C═O)(CH₂)_(p′)(C═O)—W′—D; where

W′ represents a covalent bond or a linker selected from the groupconsisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, and—NHCH(COOH)CH₂CH₂(C═O)— (the latter representing an L-gamma-Glu or aD-gamma-Glu residue);

wherein p′ represents an integer in the range of 1 to 4; and

D represents a drug substance; or

X′ represents a linker of Formula Ie′:

wherein,

represents a covalent bond towards R¹′ or R²′; or

X′ represents a linker of Formula If′:

wherein,

represents a covalent bond towards R¹′ or R²′; or

X′ represents a linker of Formula Ig′:

wherein,

represents a covalent bond towards R¹′ or R²′; or

X′ represents a linker of Formula Ih′:

wherein,

(represents a covalent bond towards R¹′ or R²′; or

X′ represents a linker of Formula Ii′:

wherein,

represents a covalent bond towards R¹′ or R²′; and

W′ represents a covalent bond, or a linker selected from the groupconsisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, or—NHCH(COOH)CH₂CH₂(C═O)— (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and

D represents a drug substance; and

R¹′ and R²′, which may be identical or different, each represents agroup of Formula IIa′ or Formula IIb′:

wherein,

one to four Y′ represents H; and

none, one or two Y′ represents F, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/orSO₂CF₃; and

one Y′ represents (a covalent bond representing) the attachment point toX′ of Formula I′; and

when X′ is Formula Ie′, If′, Iq′ or Ih′, one Y′ in either R¹′ or R²′represents —(C═O)—W′—D, where W′ represents a covalent bond, or a linkerselected from the group consisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—,—NHCH₂CH₂CH₂(C═O)—, and —NHCH(COOH)CH₂CH₂(C═O)— (the latter representingan L-gamma-Glu or a D-gamma-Glu residue); and

wherein D represents a drug substance.

The drug substance D to be conjugated according to the invention may beselected from a number of protein and peptide-based drugs, and inparticular insulin, GLP-1, and amylin, which are used in treatment ofdiabetes.

In one embodiment the diboron conjugate of the invention may inparticular be a compound according to the general Formula I′, wherein Drepresents insulin or an insulin analogue.

In another embodiment the diboron compound of the invention is acompound according to the general Formula I′, wherein D represents GLP-1or a GLP-1 analogue.

In a third embodiment the diboron compound of the invention is acompound according to the general Formula I′, wherein D representsamylin or an amylin analogue.

The diboron compound of the invention may in particular be a compoundaccording to the general Formula I′, wherein the diboron compoundrepresented by the general Formula I′ is conjugated to the drugsubstance D via a lysine (K) residue, which may be a native or anintroduced lysine residue, or to an N-terminal of the drug substance.

In another embodiment, the diboron compound of the invention may inparticular be a compound according to the general Formula I′, whereinthe diboron compound is conjugated to the drug substance D via a nativelysine (K) residue, or to an N-terminal of the drug substance.

In a third embodiment, the diboron compound of the invention may inparticular be a compound according to the general Formula I′, whereinthe diboron compound is conjugated to the drug substance D via two ormore (native and/or introduced) lysine residues, and/or one or twoN-terminals of the drug substance.

The Diboron Compounds of the Invention

In another aspect the invention provides diboron compounds, and inparticular a diboronate or a diboroxole derivative, represented byFormula I:

R¹′—X′—R²′,

in which Formula I,

X represents a linker of Formula Ia:

wherein

represents a covalent bond towards R¹ or R²;

W represents OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); or

X represents a linker of Formula Ib:

wherein,

represents a covalent bond towards R¹ or R²; and

R³ represent —(CH₂)_(m)(C═O)—W;

wherein m represents an integer in the range of 1 to 4; and

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); or

X represents a linker of Formula Ic:

which represents a D- or an L-amino acid form; and

wherein,

represents a covalent bond towards R¹ or R²;

n represents an integer in the range of 1 to 4;

W represents OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); or

wherein X represents a linker of Formula Id:

which represents a R,R or SS, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine;

wherein,

represents a covalent bond towards R¹ or R²;

R⁴ represents —(C═O)(CH₂)_(m)(C═O)—W;

wherein m represents an integer in the range of 1 to 4;

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); or

X represents a linker of Formula Ie:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula If:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula Ig:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula Ih:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula Ii:

wherein,

represents a covalent bond towards R¹ or R²; and

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one to four Y represents H; and

none, one or two Y represents F, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/orSO₂CF₃; and

one Y represents (a covalent bond representing) the attachment point toX of Formula I; and

when X is Formula Ie, If, Iq or Ih, one Y in either R¹ or R² represents—(C═O)—W, where W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH,—NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latter representing anL-gamma-Glu or a D-gamma-Glu residue).

In one embodiment, the diboron compound of the invention is representedby Formula I, wherein X represents a linker of Formula Ia:

wherein

represents a covalent bond towards R¹ or R²;

W represents OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Ia;

none, one or two of Y represent F, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃and/or SO₂CF₃; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ia asdefined above, wherein

W represents —OH.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ia asdefined above, wherein

W represents —OH;

one of Y represents F or CF₃; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ia asdefined above, wherein

W represents —OH;

one of Y represents F; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ia asdefined above, wherein

W represents —OH;

R¹ and R² are identical and represent a group of Formula IIa;

one of Y represents F; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ia asdefined above, wherein

W represents —OH;

R¹ and R² are identical and represent a group of Formula IIb;

one of Y represents F; and

the remaining Y represents H.

In another embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ib:

wherein,

represents a covalent bond towards R¹ or R²; and

R³ represent —(CH₂)_(m)(C═O)—W;

wherein m represents an integer in the range of 1 to 4; and

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue);

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Ib;

none, one or two of Y represent F, Cl, CF₂, CF₃, SF, OCF₃, SO₂CH₃ and/orSO₂CF₃; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ib asdefined above, wherein m is 1 and W is —OH.

In a third embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ic:

which represents a D- or an L-amino acid form; and

wherein,

represents a covalent bond towards R¹ or R²;

n represents an integer in the range of 1 to 4;

W represents OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Ic;

none, one or two of Y represent F, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃and/or SO₂CF₃; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ic asdefined above, wherein n is an integer in the range of 1 to 3 and W is—OH.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ic asdefined above, wherein

n is 1, 2 or 3;

W represents —OH;

R¹ and R² are identical and represent a group of Formula IIa or IIb;

one of Y represents F or CF₃; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ic asdefined above, wherein

n is 1, 2 or 3;

W represents —OH;

R¹ and R² are identical and represent a group of Formula IIa;

one of Y represents F; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ic asdefined above, wherein

n is 1 or 2;

W represents —OH;

R¹ and R² are identical and represent a group of Formula IIb;

one of Y represents F or CF₃; and

the remaining Y represents H.

In a fourth embodiment, the diboron compound of the invention isrepresented by Formula I, wherein wherein X represents a linker ofFormula Id:

which represents a R,R or SS, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine;

wherein,

represents a covalent bond towards R¹ or R²;

R⁴ represents —(C═O)(CH₂)_(p)(C═O)—W;

wherein p represents an integer in the range of 1 to 4;

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Id;

none, one or two of Y represent F, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃and/or SO₂CF₃; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Id asdefined above, wherein p is 2 and W is —OH.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Id asdefined above, wherein

p represents 2;

W represents —OH;

R¹ and R² are identical and represent a group of Formula IIb;

one of Y represents F or CF₃; and

the remaining Y represents H.

In a fifth embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ie:

wherein,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —CO— of Formula Ie;

one Y in either R¹ or R² represents —(C═O)—W, where W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing an L-gamma-Glu or a D-gamma-Glu residue);

none, one or two of Y represent F, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃and/or SO₂CF₃; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Id asdefined above, wherein W is —OH.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ie asdefined above, wherein

R¹ and R² are identical and represent a group of Formula IIa;

W represents —OH;

one Y represents —COOH or —CONHCH₂COOH;

one Y represents F or CF₃; and

the remaining of Y represents H.

In a sixth embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula If:

wherein,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —SO— of Formula If;

one Y in either R¹ or R² represents —(C═O)—W, where W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing an L-gamma-Glu or a D-gamma-Glu residue);

none, one or two of Y represent F, Cl, CF₂, CF₃, SF, OCF₃, SO₂CH₃ and/orSO₂CF₃; and

the remaining Y represents H.

In a seventh embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ig:

wherein,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —(SO₂)— of Formula Ig;

one Y in either R¹ or R² represents —(C═O)—W, where W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing an L-gamma-Glu or a D-gamma-Glu residue);

none, one or two of Y represent F, Cl, CF₂, CF₃, SF, OCF₃, SO₂CH₃ and/orSO₂CF₃; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ig asdefined above, wherein

R¹ and R² are identical and represent a group of Formula IIa;

-   -   one Y in either R¹ or R² represents —(C═O)—W, where W represents        —OH or —NHCH₂COOH;

one Y represents F, CF₃ or SF₅; and

the remaining of Y represents H.

In an eighth embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ih:

wherein,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —(CF₂)— of Formula Ih;

one Y in either R¹ or R² represents —(C═O)—W, where W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing an L-gamma-Glu or a D-gamma-Glu residue);

none, one or two of Y represent F, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃and/or SO₂CF₃; and

the remaining Y represents H.

In an further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ih asdefined above, wherein

R¹ and R² are identical and represent a group of Formula IIa;

one Y in either R¹ or R² represents —(C═O)—W, where W represents —OH or—NHCH₂COOH;

one Y represents CF₃; and

the remaining of Y represents H.

In a ninth embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ii:

wherein,

represents a covalent bond towards R¹ or R²;

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Ii;

none, one or two of Y represent F, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃and/or SO₂CF₃; and

the remaining Y represents H.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X represents a linker of Formula Ii asdefined above, wherein W is —OH.

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X is represented by Formula Ia, Ib,Ic, Id, Ie, If, Ig, Ih, or Ii as defined above, and wherein R¹ and R²,which may be identical or different, each represents a group of FormulaIIa:

wherein,

one to four Y represents H; and

none, one or two of Y represents F, Cl, CF₂, CF₃, SF, OCF₃, SO₂CH₃and/or SO₂CF₃; and

one Y represents (a covalent bond representing) the attachment point toX of Formula I; and

when X is Formula Ie, If, Ig or Ih, one Y in either R¹ or R² represents—(C═O)—W, where W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH,—NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latter representing anL-gamma-Glu or a D-gamma-Glu residue).

In a further embodiment, the diboron compound of the invention isrepresented by Formula I, wherein X is represented by Formula Ia, Ib,Ic, Id, Ie, If, Ig, Ih, or Ii as defined above, and wherein R¹ and R²,which may be identical or different, each represents a group of FormulaIIb:

wherein,

one to four Y represents H; and

none, one or two of Y represents F, Cl, CF₂, CF₃, SF, OCF₃, SO₂CH₃and/or SO₂CF₃; and

one Y represents (a covalent bond representing) the attachment point toX of Formula I; and

when X is Formula Ie, If, Iq or Ih, one Y in either R¹ or R² represents—(C═O)—W, where W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH,—NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latter representing anL-gamma-Glu or a D-gamma-Glu residue).

In a further embodiment, the diboron compound of the invention isselected from the group consisting of

-   3,5-Bis((4-borono-2-fluorobenzamido)methyl)benzoic acid;-   3,5-Bis((4-borono-3-fluorobenzamido)methyl)benzoic acid;-   N,N′-bis(4-borono-3-fluorobenzamido)-N-ethyl-glycine amide;-   (S)-2,4-bis(4-borono-3-fluorobenzamido)butanoic acid;-   N-(7-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;-   3,5-Bis((7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)    methyl) benzoic acid;-   N-(5-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;-   N-(4-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;-   N-(6-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-N-(2-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxamido)ethyl)glycine;-   N²,N⁶-Bis(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysine;-   3-Borono-5-((3-borono-4-fluorophenyl)sulfonyl)-4-fluorobenzoic acid;-   3-Borono-5-(3-borono-5-fluorobenzoyl)benzoic acid;-   3-Borono-5-(5-borono-2,4-difluorobenzoyl)benzoic acid;-   N⁶-(4-Borono-2-fluorobenzoyl)-N²-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]-oxaborole-5-carbonyl)-L-lysine;-   (S)-2,3-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanoic    acid;-   (S)-2,3-Bis(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanoic    acid;-   (S)-2,3-Bis(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanoic    acid;-   (3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)difluoromethyl)benzoyl)    glycine;-   (3-Borono-5-(3-borono-5-(trifluoromethyl)benzoyl)benzoyl)glycine;-   (3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)sulfonyl)glycine;-   4-((3S,4S)-3,4-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoic    acid;-   (3-Borono-5-(3-borono-5-fluorobenzoyl)benzoyl)glycine;-   (3-(6-Borono-2-(ethoxycarbonyl)-8-fluoro-1,1-dioxido-4H-benzo[b][1,4]thiazin-4-yl)-5-fluorophenyl)boronic    acid;-   (3-Borono-5-((3-borono-5-fluorophenyl)sulfonyl)benzoyl)glycine;-   N-(1-Hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-ethyl)glycine;-   (S)-2,3-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoic    acid;-   4-((3S,4S)-3,4-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoic    acid;-   (3-Borono-5-((3-borono-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl)benzoyl)    glycine;-   4-[(3R,4R)-3,4-bis[[1-hydroxy-4-(trifluoromethyl)-3H-2,1-benzoxaborole-6-carbonyl]-amino]pyrrolidin-1-yl]-4-oxobutanoic    acid;-   2-((Bis(3-borono-5-(trifluoromethyl)phenyl)(oxo)-λ6-sulfanylidene)amino)acetic    acid;-   N-(4-(Difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-ethyl)glycine;-   N-(4-Chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;-   3-(2,3-Bis(4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanamido)propanoic    acid;-   2-((Bis(3-borono-5-(difluoromethyl)phenyl)(oxo)-λ6-sulfanylidene)amino)acetic    acid;-   2-((Bis(3-borono-5-chlorophenyl)(oxo)-λ6-sulfanylidene)amino)acetic    acid; and-   2-((Bis(3-boronophenyl)(oxo)-λ6-sulfanylidene)amino)acetic acid.

Medical Use

Viewed from another aspect the invention provides novel diboronconjugates for use as medicaments, and in particular for use asmedicaments for the treatment of metabolic disorders or conditions.

It is found that the binding constant of the diboron compounds of theinvention toward glucose is in the low millimolar range (with a Kd inthe range of 0.2-5 mM), thus matching the physiological range of glucosefluctuations (1-30 mM), in particular the glucose range where protectionagainst low blood sugar is desired (1-5 mM).

While the diboroxole compounds are found to provide the best selectivityfor glucose vs lactate (see Table 1), the diboronate compounds also holdpotential, as blood lactate values do not fluctuate as much, or go ashigh as glucose values.

Pharmaceutical Compositions

Viewed from another aspect the invention provides novel pharmaceuticalcompositions comprising a therapeutically effective amount of a diboronconjugate of the invention. In one embodiment, the invention provides apharmaceutical composition comprising a diboron conjugate of theinvention and one or more excipients.

Intermediate Compounds

Viewed from another aspect the invention provides novel diboroncompounds for use as an intermediate compound in the manufacture of thenovel diboron conjugates of the invention.

Therefore, in one embodiment, the invention relates to the use of adiboron compound, and in particular a diboronate or a diboroxolecompound represented by Formula I, as a starting material for themanufacture of the diboron conjugate of the invention.

Methods of Preparation

The diboron compounds of the invention may be prepared by conventionalmethods for chemical synthesis, e.g. those described in the workingexamples.

The diboron compounds of the invention may subsequently be use as astarting material for the preparation of the diboron conjugates of theinvention.

Methods of Therapy

Viewed from another aspect the invention provides methods of treatment,prevention or alleviation of a metabolic disease or a disorder or acondition of a living animal body, which method comprises the step ofadministering to such a living animal body in need thereof, atherapeutically effective amount of the diboron conjugate of theinvention.

PARTICULAR EMBODIMENTS

The invention is further described by the following non-limitingembodiments:

1. A diboron conjugate represented by the general Formula I′

R¹—X—R²

in which Formula I′, X, R¹ and R², are as defined herein.

2. A diboron compound represented by Formula I

R¹—X—R²

in which Formula I,

X represents a linker of Formula Ia:

wherein

represents a covalent bond towards R¹ or R²;

W represents —OH or —NHCH₂COOH; or

X represents a linker of Formula Ib:

wherein,

represents a covalent bond towards R¹ or R²; and

R³ represent —(CH₂)_(m)COOH;

wherein m represents an integer in the range 1-4; or

X represents a linker of Formula Ic:

which represents a D- or an L-amino acid form; and

wherein,

represents a covalent bond towards R¹ or R²;

n represents an integer in the range 1-4;

W represents —OH or —NHCH₂COOH; or

wherein X represents a linker of Formula Id:

which represents a R,R or SS, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine;

wherein,

represents a covalent bond towards R¹ or R²;

R⁴ represents —(C═O)(CH₂)_(m)(COOH);

wherein m represents an integer in the range 1-4; or

X represents a linker of Formula Ie:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula If:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula Ig:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula Ih:

wherein,

represents a covalent bond towards R¹ or R²; and

in which Formulas Ia, Ib, Ic, Id, Ie, If, Ig and Ih,

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one to four Y represents H; and

none, one or two of Y represents F, CF₃, and/or SF₅; and

one Y represents (a covalent bond representing) the attachment point toX of Formula I; and

in Formulas Ie, If, Iq and Ih, Y represents —COOH or CONHCH₂COOH.

3. The diboron compound of embodiment 2, represented by Formula I,wherein represents a linker of Formula Ia:

wherein

represents a covalent bond towards R¹ or R²;

W represents —OH or —NHCH₂COOH; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Ia;

none, one or two of Y represent F, CF₃, and/or SF₅; and

the remaining Y represents H.

4. The diboron compound of embodiment 2, represented by Formula I,wherein X represents a linker of Formula Ib:

wherein.

represents a covalent bond towards R¹ or R²; and

R³ represent —(CH₂)_(m)COOH;

wherein m represents an integer in the range 1-4; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Ib;

none, one or two of Y represent F, CF₃, and/or SF₅; and

the remaining Y represents H.

5. The diboron compound of embodiment 2, represented by Formula I,wherein X represents a linker of Formula Ic:

which represents a D- or an L-amino acid form; and

wherein,

represents a covalent bond towards R¹ or R²;

n represents an integer in the range 1-4;

W represents —OH or —NHCH₂COOH; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Ic;

none, one or two of Y represent F, CF₃, and/or SF₅; and

the remaining Y represents H.

6. The diboron compound of embodiment 2, represented by Formula I,wherein X represents a linker of Formula Id:

which represents a R,R or SS, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine;

wherein,

represents a covalent bond towards R¹ or R²;

R⁴ represents —(C═O)(CH₂)_(m)(COOH);

wherein m represents an integer in the range 1-4; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Id;

none, one or two of Y represent F, CF₃, and/or SF₅; and

the remaining Y represents H.

7. The diboron compound of embodiment 2, represented by Formula I,wherein X represents a linker of Formula Ie:

wherein,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —CO— of Formula Ie;

one Y represents —COOH or —CONHCH₂COOH;

none, one or two of Y represent F, CF₃, and/or SF₅; and

the remaining of Y represents H.

8. The diboron compound of embodiment 2, represented by Formula I,wherein X represents a linker of Formula If:

wherein,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —SO— of Formula If;

one Y represents —COOH or —CONHCH₂COOH;

none, one or two of Y represent F, CF₃, and/or SF₅; and

the remaining Y represents H.

9. The diboron compound of embodiment 2, represented by Formula I,wherein X represents a linker of Formula Ig:

where,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —(SO₂)— of Formula Ig;

one Y represents —COOH or —CONHCH₂COOH;

none, one or two of Y represent F, CF₃, and/or SF₅; and

the remaining Y represents H.

10. The diboron compound of embodiment 2, represented by Formula I,wherein X represents a linker of Formula Ih:

wherein,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —(CF₂)— X of Formula Ih;

one Y represents —COOH or —CONHCH₂COOH;

none, one or two of Y represent F, CF₃, and/or SF₅; and

the remaining Y represents H.

11. A diboron compound selected from the group consisting of3,5-Bis((4-borono-2-fluorobenzamido)methyl)benzoic acid;3,5-Bis((4-borono-3-fluorobenzamido)methyl)benzoic acid;N,N′-bis(4-borono-3-fluorobenzamido)-N-ethyl-glycine amide;(S)-2,4-bis(4-borono-3-fluorobenzamido)butanoic acid;N-(7-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;3,5-Bis((7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)methyl) benzoic acid;N-(5-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;N-(4-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;N-(6-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-N-(2-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxamido)ethyl)glycine;N²,N⁶-Bis(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysine;3-Borono-5-((3-borono-4-fluorophenyl)sulfonyl)-4-fluorobenzoic acid];3-Borono-5-(3-borono-5-fluorobenzoyl)benzoic acid;3-Borono-5-(5-borono-2,4-difluorobenzoyl)benzoic acid;N⁶-(4-Borono-2-fluorobenzoyl)-N²-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysine;(S)-2,3-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo-[c][1,2]oxaborole-6-carboxamido)-propanoicacid;(S)-2,3-Bis(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanoicacid;(S)-2,3-Bis(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanoicacid;(3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)difluoromethyl)benzoyl)glycine;(3-Borono-5-(3-borono-5-(trifluoromethyl)benzoyl)benzoyl)glycine;(3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)sulfonyl)glycine;4-((3S,4S)-3,4-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoicacid; (3-Borono-5-(3-borono-5-fluorobenzoyl)benzoyl)glycine;(3-(6-Borono-2-(ethoxycarbonyl)-8-fluoro-1,1-dioxido-4H-benzo[b][1,4]thiazin-4-yl)-5-fluorophenyl)boronicacid; (3-Borono-5-((3-borono-5-fluorophenyl)sulfonyl)benzoyl)-glycine;N-(1-Hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-ethyl)glycine;(S)-2,3-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid;4-((3S,4S)-3,4-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-pyrrolidin-1-yl)-4-oxobutanoicacid;(3-Borono-5-((3-borono-5-(pentafluoro-λ⁶-sulfanyl)-phenyl)sulfonyl)benzoyl)glycine; and4-[(3R,4R)-3,4-bis[[1-hydroxy-4-(trifluoro-methyl)-3H-2,1-benzoxaborole-6-carbonyl]-amino]pyrrolidin-1-yl]-4-oxobutanoicacid.

12. The diboron conjugate of embodiment 1 for use as a medicament.

13. The diboron compound of any one of embodiments 2-11 for use as anintermediate compounds for the manufacture of the diboron conjugateaccording to embodiment 1.

14. A method of treatment, prevention or alleviation of a metabolicdisease or a disorder or a condition of a living animal body, whichmethod comprises the step of administering to such a living animal bodyin need thereof, a therapeutically effective amount of the diboronconjugate of embodiment 1.

The invention is even further described by the following non-limitingembodiments:

15. A diboron conjugate represented by the general Formula I′

R¹′—X′—R²′

in which Formula I′,

X′ represents a linker of Formula Ia′:

wherein,

represents a covalent bond towards R¹′ or R²′;

D represents a drug substance; and

W′ represents a covalent bond, or a linker selected from the groupconsisting of

—NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, and—NHCH(COOH)CH₂CH₂(C═O)— (the latter representing a L-gamma-Glu orD-gamma-Glu residue); or

X′ represents a linker of Formula Ib′:

wherein,

represents a covalent bond towards R¹′ or R²′; and

R³′ represent —(CH₂)(C═O)—W′—D, wherein

m′ represents an integer in the range of 1 to 4;

W′ represents a covalent bond or a linker selected from the groupconsisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, and—NHCH(COOH)CH₂CH₂(C═O)— (the latter representing a L-gamma-Glu orD-gamma-Glu residue); and

D represents a drug substance; or

X′ represents a linker of Formula Ic′:

which represents a D- or an L-amino acid form; and

wherein,

represents a covalent bond towards R¹′ or R²′;

n′ represents an integer in the range of 1 to 4;

W′ represents a covalent bond or a linker selected from the groupconsisting of

—NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, and—NHCH(COOH)CH₂CH₂(C═O)— (the latter representing a L-gamma-Glu orD-gamma-Glu residue); and

D represents a drug substance; or

X′ represents a linker of Formula Id′:

which represents a R,R or SS, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine;

wherein,

represents a covalent bond towards R¹′ or R²′;

R⁴′ represents —(C═O)(CH₂)_(p′)(C═O)—W′—D; where

W′ represents a covalent bond or a linker selected from the groupconsisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, and—NHCH(COOH)CH₂CH₂(C═O)—

(the latter representing a L-gamma-Glu or D-gamma-Glu residue);

wherein p′ represents an integer in the range of 1 to 4;

and

D represents a drug substance; or

X′ represents a linker of Formula Ie′:

wherein,

represents a covalent bond towards R¹′ or R²′; or

X′ represents a linker of Formula If′:

wherein,

represents a covalent bond towards R¹′ or R²′; or

X′ represents a linker of Formula Ig′:

wherein,

represents a covalent bond towards R¹′ or R²′; or

X′ represents a linker of Formula Ih′:

wherein,

represents a covalent bond towards R¹′ or R²′; or

X′ represents a linker of Formula Ii′:

wherein,

represents a covalent bond towards R¹, or R²; and

one to four Y′ represents H; and

none, one or two Y′ represents F, Cl, CF₂, CF₃, and/or SF₅; and

one Y′ represents (a covalent bond representing) the attachment point toX′ of Formula I′; and

when X′ is Formula Ie′, If′, Iq′ or Ih′, one Y in either R¹′ or R²′represents —(C═O)—W′—D, where W′ represents a covalent bond, or a linkerselected from the group consisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—,—NHCH₂CH₂CH₂(C═O)—, and —NHCH(COOH)CH₂CH₂(C═O)— (the latter representinga L-gamma-Glu or D-gamma-Glu residue); and

wherein D represents a drug substance.

16. A diboron compound represented by Formula I

R¹—X—R²

in which Formula I,

X represents a linker of Formula Ia:

wherein

represents a covalent bond towards R¹ or R²;

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing a L-gamma-Glu orD-gamma-Glu residue); or

X represents a linker of Formula Ib:

wherein,

represents a covalent bond towards R¹ or R²; and

R³ represent —(CH₂)_(m)(C═O)—W;

wherein m represents an integer in the range of 1 to 4; and

W represents OH, NHCH₂COOH; NHCH₂CH₂COOH; NHCH₂CH₂CH₂COOH; orNHCH(COOH)CH₂CH₂COOH (the latter representing a L-gamma-Glu orD-gamma-Glu residue); or

X represents a linker of Formula Ic:

which represents a D- or an L-amino acid form; and

wherein,

represents a covalent bond towards R¹ or R²;

n represents an integer in the range of 1 to 4;

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing a L-gamma-Glu orD-gamma-Glu residue); or

wherein X represents a linker of Formula Id:

which represents a R,R or SS, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine;

wherein,

represents a covalent bond towards R¹ or R²;

R⁴ represents —(C═O)(CH₂)_(p)(C═O)—W;

wherein p represents an integer in the range of 1 to 4;

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing a L-gamma-Glu orD-gamma-Glu residue); or

X represents a linker of Formula Ie:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula If:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula Ig:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula Ih:

wherein,

represents a covalent bond towards R¹ or R²; or

X represents a linker of Formula Ii:

wherein,

represents a convalent bond towards R¹ or R²; and

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing a L-gamma-Glu orD-gamma-Glu residue); and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one to four Y represents H; and

none, one or two of Y represents F, Cl, CF₂, CF₃, and/or SF₅; and

one Y represents (a covalent bond representing) the attachment point toX of Formula I; and

when X is Formula Ie, If, Iq or Ih, one Y in either R¹ or R² represents—(C═O)—W, where W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH,—NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latter representing aL-gamma-Glu or D-gamma-Glu residue).

17. The diboron compound of embodiment 16, represented by Formula I,wherein X represents a linker of Formula Ia:

wherein

represents a covalent bond towards R¹ or R²;

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing a L-gamma-Glu orD-gamma-Glu residue); and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Ia;

none, one or two of Y represent F, Cl, CF₂, CF₃, and/or SF₅; and

the remaining Y represents H.

18. The diboron compound of embodiment 16, represented by Formula I,wherein X represents a linker of Formula Ib:

wherein,

represents a covalent bond towards R¹ or R²; and

R³ represent —(CH₂)_(m)(C═O)—W;

wherein m represents an integer in the range of 1 to 4;

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH; or—NHCH(COOH)CH₂CH₂COOH (the latter representing a L-gamma-Glu orD-gamma-Glu residue); and

-   -   R¹ and R², which may be identical or different, each represents        a group of Formula IIa or IIb;

wherein

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Ib;

none, one or two of Y represent F, Cl, CF₂, CF₃, and/or SF₅; and

the remaining Y represents H.

19. The diboron compound of embodiment 16, represented by Formula I,wherein X represents a linker of Formula Ic:

which represents a D- or an L-amino acid form; and

wherein,

represents a covalent bond towards R¹ or R²;

n represents an integer in the range of 1 to 4;

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing a L-gamma-Glu orD-gamma-Glu residue); and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Ic;

none, one or two of Y represent F, Cl, CF₂, CF₃, and/or SF₅; and

the remaining Y represents H.

20. The diboron compound of embodiment 16, represented by Formula I,wherein X represents a linker of Formula Id:

which represents a R,R or SS, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine;

wherein,

represents a covalent bond towards R¹ or R²;

R⁴ represents —(C═O)(CH₂)_(p)(C═O)—W;

wherein p represents an integer in the range of 1 to 4;

W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing a L-gamma-Glu orD-gamma-Glu residue); and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

One Y represents (a covalent bond representing) the attachment point tothe linker X of Formula Id;

none, one or two of Y represent F, Cl, CF₂, CF₃, and/or SF₅; and

the remaining Y reprints H.

21. The diboron compound of embodiment 16, represented by Formula I,wherein X represents a linker of Formula Ie:

wherein

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —CO— of Formula Ie;

one Y in either R¹ or R² represents —(C═O)—W, where W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing a L-gamma-Glu or D-gamma-Glu residue);

none, one or two of Y represent F, Cl, CF₂, CF₃, and/or SF₅; and

the remaining of Y represents H.

22. The diboron compound of embodiment 16, represented by Formula I,wherein X represents a linker of Formula If:

wherein,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —SO— of Formula If;

one Y in either R¹ or R² represents —(C═O)—W, where W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing a L-gamma-Glu or D-gamma-Glu residue);

none, one or two of Y represent F, Cl, CF₂, CF₃, and/or SF₅; and

the remaining Y represents H.

23. The diboron compound of embodiment 16, represented by Formula I,wherein X represents a linker of Formula Ig:

wherein,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,

one Y represents (a covalent bond representing) the attachment point tothe linker —(SO₂)— of Formula Ig;

one Y in either R¹ or R² represents —(C═O)—W, where W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing a L-gamma-Glu or D-gamma-Glu residue);

none, one or two of Y represent F, Cl, CF₂, CF₃, and/or SF₅; and

the remaining Y represents H.

24. The diboron compound of embodiment 16, represented by Formula I,wherein X represents a linker of Formula Ih:

wherein,

represents a covalent bond towards R¹ or R²; and

R¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein

one Y represents (a covalent bond representing) the attachment point tothe linker —(CF₂)— of Formula Ih;

one Y in either R¹ or R² represents —(C═O)—W, where W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing a L-gamma-Glu or D-gamma-Glu residue);

none, one or two of Y represent F, Cl, CF₂, CF₃, and/or SF₅; and

the remaining Y represents H.

25. The diboron compound of embodiment 16, represented by Formula I,wherein X represents a linker of Formula Ii:

wherein,

represents a covalent bond towards R¹ or R²;W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or—NHCH(COOH)CH₂CH₂COOH (the latter representing a L-gamma-Glu orD-gamma-Glu residue); andR¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein,one Y represents (a covalent bond representing) the attachment point tothe linker X of Formula II;none, one or two of Y represent F, Cl, CF₂, CF₂, and or SF₅; andthe remaining Y represents H.

26. A diboron compound selected from the group consisting of3,5-Bis((4-borono-2-fluorobenzamido)methyl)benzoic acid;3,5-Bis((4-borono-3-fluoro-benzamido)methyl)benzoic acid;N,N′-bis(4-borono-3-fluorobenzamido)-N-ethyl-glycine amide;(S)-2,4-bis(4-borono-3-fluorobenzamido)butanoic acid;N-(7-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;3,5-Bis((7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)methyl)benzoic acid;N-(5-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;N-(4-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;N-(6-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-N-(2-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxamido)ethyl)glycine;N²,N⁶-Bis(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysine;3-Borono-5-((3-borono-4-fluorophenyl)sulfonyl)-4-fluorobenzoic acid;3-Borono-5-(3-borono-5-fluorobenzoyl)benzoic acid;3-Borono-5-(5-borono-2,4-difluorobenzoyl)benzoic acid;N⁶-(4-Borono-2-fluorobenzoyl)-N²-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]-oxaborole-5-carbonyl)-L-lysine;(S)-2,3-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo-[c][1,2]oxaborole-6-carboxamido)propanoicacid;(S)-2,3-Bis(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid;(S)-2,3-Bis(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoic acid;(3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)difluoromethyl)benzoyl)-glycine;(3-Borono-5-(3-borono-5-(trifluoromethyl)benzoyl)benzoyl)glycine;(3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)sulfonyl)glycine;4-((3S,4S)-3,4-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoicacid; (3-Borono-5-(3-borono-5-fluorobenzoyl)benzoyl)glycine;(3-(6-Borono-2-(ethoxy-carbonyl)-8-fluoro-1,1-dioxido-4H-benzo[b][1,4]thiazin-4-yl)-5-fluorophenyl)boronicacid; (3-Borono-5-((3-borono-5-fluorophenyl)sulfonyl)benzoyl)glycine;N-(1-Hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;(S)-2,3-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid;4-((3S,4S)-3,4-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoicacid;(3-Borono-5-((3-borono-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl)benzoyl)glycine;2-Bis(3-borono-5-(trifluoromethyl)phenyl)(oxo)-6-sulfanylidene)amino)aceticacid;N-(4-(Difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)-glycine;N-(4-Chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;3-(2,3-Bis(4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanamido)propanoicacid;2-((Bis(3-borono-5-(difluoromethyl)phenyl)(oxo)-6-sulfanylidene)amino)aceticacid; 2-((Bis(3-borono-5-chlorophenyl)(oxo)-6-sulfanylidene)amino)aceticacid; and 2-((Bis(3-boronophenyl)(oxo)-6-sulfanylidene)-amino)aceticacid.

27. The diboron conjugate of anyone of embodiments 15-26 for use as amedicament.

28. The diboron compound of any one of embodiments 15-26 for use as anintermediate compounds for the manufacture of the diboron conjugateaccording to embodiment 15.

29. A method of treatment, prevention or alleviation of a metabolicdisease or a disorder or a condition of a living animal body, whichmethod comprises the step of administering to such a living animal bodyin need thereof, a therapeutically effective amount of the diboronconjugate of anyone of embodiments 15-26.

EXAMPLES

The invention is further illustrated with reference to the followingexamples, which are not intended to be in any way limiting to the scopeof the invention as claimed.

ABBREVIATIONS USED HEREIN

-   AA acetic acid-   AIBN 2,2′-azobis(2-methylpropionitrile)-   ARS Alizarin Red Sodium-   DAST (diethylamino)sulfur trifluoride-   DCC N,N′-dicyclohexylcarbodiimide-   DMSO dimethylsulfoxide-   EDC N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide-   ELSD electrospray detection-   F-NMR fluorine-19 nuclear magnetic resonance spectroscopy-   FA formic acid-   HATU    1-((dimethylamino)(dimethyliminio)methyl)-1H-[1,2,3]triazolo[4,5-b]pyridine    3-oxide hexafluorophosphate-   HSA human serum albumin-   LCMS liquid chromatography mass spectrometry-   NBS N-bromosuccinimide (1-bromopyrrolidine-2,5-dione)-   NIS N-iodosuccinimide (1-iodobromopyrrolidine-2,5-dione)-   NMR nuclear magnetic resonance spectroscopy-   HOSu, NOHSu N-hydroxysuccinimide-   PCC pyridinium chlorochromate-   XPhos 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl

Preparation of Diboron Compounds of the Invention Example 13,5-Bis((4-borono-2-fluorobenzamido)methyl)benzoic acid

3,5-Bis((4-borono-2-fluorobenzamido)methyl)benzoic acid was synthesizedaccording to the reaction schemes shown in Chem. 1 and Chem. 2 andfollowing the procedure described below.

3,5-Dimethylbenzoic acid (4, 27.6 g, 18.4 mmol) was suspended inmethanol (80 mL) and treated with concentrated sulfuric acid (8 mL). Themixture was refluxed for 2 days. After neutralization with sodiumcarbonate (50 g), the mixture was dissolved in water (250 mL) andextracted with diethyl ether (2×300 mL). The organic phases were driedover anhydrous sodium sulfate, filtered and evaporated to drynessaffording methyl 3,5-dimethylbenzoate 5 as pale yellow oil.

Yield: 29.3 g (97%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.67 (s, 2H); 7.19 (s, 1H);3.91 (s, 3H); 2.37 (s, 6H).

A mixture of the above methyl 3,5-dimethylbenzoate (5, 29.3 g, 178mmol), N-bromosuccinimide (NBS, 111 g, 623 mmol) and a spatula ofazobisisobutyronitrile in methyl formate (450 mL) was irradiated withvisible light while heating to reflux for 20 hours. The solvent wasevaporated and the residue was dissolved in dichloromethane (200 mL).The precipitated succinimide was filtered off and the filtrate waswashed with saturated aqueous solution of sodium sulfite (2×150 mL). Theorganic layer was dried over anhydrous sodium sulfate, filtered andevaporated. The residue was purified by flash column chromatography(Silicagel 60, 0.040-0.063 mm; eluent: hexane/ethyl acetate 15:1). Theproduct was crystallized from ethyl acetate/cyclohexane mixture givingmethyl 3,5-bis(bromomethyl)benzoate 6 as white solid.

Yield: 25.6 g (45%).

R_(F) (SiO₂, hexanes/ethyl acetate 9:1): 0.50.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.02-7.95 (m, 2H); 7.62 (s,1H); 4.51 (s, 4H); 3.94 (s, 3H).

A suspension of the above bromide 6 (25.3 g, 78.6 mmol) and sodiumdiformylamide (20.9 g, 220 mmol) in dry acetonitrile (350 mL) wasrefluxed for 4 hours. After removal of a white solid by filtration, thesolvent was evaporated. Recrystallization from ethyl acetate/cyclohexanemixture afforded methyl 3,5-bis((N-formylformamido)methyl)benzoate 7 aswhite powder.

Yield: 21.0 g (88%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.08 (s, 4H); 7.72 (s, 2H);7.44 (s, 1H); 4.70 (s, 4H); 3.84 (s, 3H).

Benzoate (7, 20.9 g, 68.5 mmol) was dissolved in a mixture of1,4-dioxane (220 mL) and concentrated hydrochloric acid (280 mL) andheated for 2 hours to reflux.

After cooling down to room temperature, a flow of air was passed throughthe solution. Product began to precipitate. After 1 hour, the solventwas evaporated and product was recrystallized from methanol/diethylether mixture affording 3,5-bis(aminomethyl) benzoic aciddihydrochloride 8 as white powder.

Yield: 17.1 g (98%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 13.26 (bs, 1H); 8.65 (bs,6H); 8.10 (s, 2H); 7.88 (s, 1H); 4.08 (s, 4H).

Mixture of 4-borono-2-fluorobenzoic acid (1, 1.14 g, 6.20 mmol), pinacol(0.74 g, 6.20 mmol) and molecular sieves (2.60 g) in dry toluene (40 mL)was stirred overnight at room temperature. The suspension was filtered;solid residue was suspended in dichloromethane (50 mL). Subsequentlyhydroxysuccinimide (HOSu, 1.43 g, 12.4 mmol) andN-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC.HCl,2.38 g, 12.4 mmol) were added. Resulting mixture was stirred overnightat room temperature. The suspension was filtered and the filtrate waspartitioned between ethyl acetate (80 mL) and 0.1 M aqueous solution ofhydrochloric acid (50 mL). Organic layer was washed with 0.1 M aqueoussolution of hydrochloric acid (2×75 mL) and brine (1×75 mL), dried overanhydrous sodium sulfate, filtered and evaporated to yield2,5-dioxopyrrolidin-1-yl2-fluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate (2) aswhite powder.

Yield: 1.36 g (62%).

¹H NMR spectrum (400 MHz, CDCl₃, δ_(H)): 8.07-8.03 (m, 1H); 7.69-7.65(m, 1H); 7.65-7.60 (m, 1H); 2.92 (bs, 4H); 1.37 (s, 12H).

3,5-Bis(aminomethyl)benzoic acid dihydrochloride (3, 152 mg, 0.60 mmol)was dissolved in water (2 mL). Subsequently N,N-diisopropylethylamine(0.04 mL, 0.24 mmol), N,N-dimethylformamide (4 mL) and2,5-dioxopyrrolidin-1-yl2-fluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate (2,0.44 g, 1.20 mmol) were added. The mixture was stirred overnight at roomtemperature; then solvent was evaporated. The liquid residue wasdissolved in aqueous trifluoroacetic acid (50%, 10 mL) and stirredovernight at 90° C. Precipitate was collected by filtration and washedwith acetonitrile to yield the title compound (4) as white powder.

Yield: 105 mg (35%).

¹H NMR spectrum (400 MHz, DMSO-d₆, δ_(H)): 12.94 (bs, 1H); 9.03-8.88 (m,2H); 8.36 (s, 4H); 7.83 (s, 2H); 7.67-7.53 (m, 7H); 4.51 (d, J=5.9 Hz,4H).

LC-MS purity: 99% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 2.21 min.

LC-MS m/z: 513.4 (M+H)⁺.

Example 2 3,5-Bis((4-borono-3-fluorobenzamido)methyl)benzoic acid

3,5-Bis((4-borono-3-fluorobenzamido)methyl)benzoic acid was preparedsimilarly to the compound of Example 1 from 4-borono-3-fluorobenzoicacid.

Example 3 N,N′-bis(4-borono-3-fluorobenzamido)-N-ethyl-glycine amide

N,N′-bis(4-borono-3-fluorobenzamido)-N-ethyl-glycine amide was preparedsimilar to the compound of Example 5 from 4-borono-3-fluorobenzoic acid.

Example 4 (S)-2,4-bis(4-borono-3-fluorobenzamido)butanoic acid

(S)-2,4-bis(4-borono-3-fluorobenzamido)butanoic acid was synthesizedaccording to the reaction scheme shown in Chem. 3 and following theprocedure described below.

L-2,4-Diaminobutyric acid dihydrochloride (0.20 g, 1.69 mmol) wasdissolved in water (3.6 mL). Subsequently N,N-diisopropylethylamine(1.18 mL, 6.76 mmol), N,N-dimethylformamide (7.2 mL) and2,5-dioxopyrrolidin-1-yl3-fluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate (1,1.23 g, 3.38 mmol) were added. The mixture was stirred overnight at roomtemperature; then it was acidified by 1 M aqueous solution ofhydrochloric acid. The solvent was co-evaporated with toluene threetimes. The residue was dissolved in dichloromethane/toluene mixture(1:1, 100 mL). The residue was dissolved in ethyl acetate (60 mL) andwashed with water (3×40 mL). Organic layer was dried over anhydroussodium sulfate, filtered and evaporated. The residue was dissolved indichloromethane (3 mL) and product started to precipitate. Cyclohexanewas added (35 mL). The precipitate was collected by filtration, washedwith cyclohexane and dried in vacuo to yield2,4-bis(4-(1,3,2-dioxaborolan-2-yl)-3-fluorobenzamido)butanoic acid (2)as transparent oil.

Yield: 960 mg (92%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.90-7.75 (m, 2H); 7.65-7.40(m, 5H); 7.11-7.02 (m, 1H); 4.91-4.79 (m, 1H); 3.58-3.50 (s, 2H);2.10-1.70 (m, 4H); 1.36 (s, 24H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 05:95 to100:0+0.1% FA): 2.82 min, 3.56 min, 4.53 min.

LC-MS m/z: 615.6 (M+H)+, 533.5 (M+H-pinacol)+, 451.4 (M+H−2×pinacol)+.

The above acid (2, 200 mg, 0.32 mmol) was dissolved in tetrahydrofuran(3 mL) and water (0.75 mL). Sodium metaperiodate (0.35 g, 1.63 mmol) wasadded and the resulting mixture was vigorously stirred at ambienttemperature (24° C.) for 2 hours and the resulting suspension wasevaporated in vacuo. The residue was purified by preparative LC/MS(SunFire Prep C18, 5 μm, 19×100 mm, acetonitrile/water 5:95 to100:0+0.1% FA) to give the title compound (3) as white solid.

Yield: 50.0 mg (26%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 8.73 (d, J=7.5 Hz, 1H); 8.58(t, J=5.5 Hz, 1H); 8.35 (d, J=7.9 Hz, 4H); 7.70-7.50 (m, 6H); 4.49-4.42(m, 1H); 3.54-3.43 (m, 2H); 2.19-1.95 (m, 2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 2.80 min.

LC-MS m/z: 450.4 (M+H)⁺.

Example 5N-(7-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine

N-(7-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycinewas synthesized according to the reaction schemes shown in Chem. 4 andChem. 5 and following the procedure described below.

Ethane-1,2-diamine (2, 44.0 mL, 659 mmol) was dissolved in anhydrousdichloromethane (300 mL) and tert-butyl 2-bromoacetate (1, 11.0 mL, 81.7mmol) in anhydrous dichloromethane (20 mL) was added using syringe pump(3 mL/hour) at 0° C. under argon atmosphere. The reaction mixture wasstirred for 10 hours at room temperature. Resulting mixture wasextracted with water (200 mL), organic phase was dried with anhydroussodium sulfate and concentrated under reduced pressure. Residue wasdissolved in cold diethyl ether (150 mL) and precipitated with 3 Msolution of hydrogen chloride in diethyl ether to give tert-butyl(2-aminoethyl)glycinate hydrochloride (3) as white solid.

Yield: 10.8 g (63%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 3.31 (s, 2H); 2.83-2.75 (m,2H); 2.73-2.64 (m, 2H); 1.47 (s, 9H).

7-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid(2, 0.30 g, 1.53 mmol) was dissolved in N,N-dimethylformamide (15 mL)and1-((dimethylamino)(dimethyliminio)methyl)-1H-[1,2,3]triazolo[4,5-b]pyridine3-oxide hexafluorophosphate(V) (HATU, 0.58 g, 1.53 mmol) andN,N-diisopropylethylamine (1.06 mL, 6.12 mmol) were added. After 5minutes, tert-butyl (2-aminoethyl)glycinate hydrochloride (1, 0.16 g,0.77 mmol) was added to the reaction mixture at room temperature and thereaction was stirred for 16 hours. Volatiles were then evaporated underreduced pressure and the ester 3 was used for the next step withoutfurther purification.

LC-MS purity: 40% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.48 min.

LC-MS m/z: 531.7 (M+H)⁺.

tert-ButylN-(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycinate (3, <0.77 mmol) was dissolved in 5.2 M solution ofhydrogen chloride in 1,4-dioxane (10 mL) and the mixture was stirred for2 hours at room temperature. Volatiles were then evaporated underreduced pressure and the residue was purified by preparative HPLC(Column X-Bridge, C18, 15 μm; 50×250 mm; acetonitrile/water 3:97 to30:70+0.05% AA) and freeze-dried to affordN-(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine4 as white solid.

Yield: 81 mg (22%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.41-9.33, 2H); 8.42-8.18 (m,1H); 7.81-7.64 (m, 1H); 7.43-7.11 (m, 3H); 5.07-4.97 (m, 4H); 4.22 (s,1H); 3.98 (s, 1H); 3.68 (t, J=6.5 Hz, 1H); 3.60-3.40 (m, 3H).

LC-MS purity: 96% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 2.98 min.

LC-MS m/z: 475.5 (M+H)⁺.

Example 63,5-Bis((7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)methyl)benzoic acid

3,5-Bis((7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)methyl)benzoic acid was synthesized according to the reaction scheme shown inChem. 6 and following the procedure described below.

Butyllithium (2.35 M in hexane, 53.0 ml, 125 mmol) was drop-wise addedto an nitrogen purged solution of 2,2,6,6-tetramethylpiperidine (17.7 g,125 mmol) in anhydrous tetrahydrofuran (100 mL) over 20 minutesmaintaining internal temperature below −35° C. A solution of2-fluoro-4-methylbenzonitrile (1, 15.0 g, 111 mmol) in drytetrahydrofuran (50 mL) was drop-wise added to the above mixture at arate keeping internal temperature below −70° C. Then the mixture waswarmed up to −50° C. for 45 minutes. A solution of iodine (31.0 g, 122mmol) in tetrahydrofuran (50 mL) was drop-wise added to the reactionmixture keeping internal temperature below −60° C. The mixture wasstirred for 12 hours at ambient temperature, then it was quenched bypouring to a stirred solution of sodium thiosulfate (10 g) in water (500mL). The mixture was stirred for 1 hour. The mixture was treated withethyl acetate (300 mL), aqueous phase was separated and re-extracted(100 mL). Combined organics were dried over anhydrous sodium sulfate andevaporated. The residue was loaded on silica by co-evaporation andcolumn chromatography (Silicagel 60, 0.063-0.200 mm; eluent:cyclohexane/diethyl ether 10:1) afforded crude product, which wascrystallized from methanol to give 2-fluoro-3-iodo-4-methylbenzonitrile(2) as a white crystalline solid.

Yield: 18.49 g (64%).

R_(F) (SiO₂, cyclohexane/diethyl ether 9:1): 0.35

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.48 (dd, J=7.9 and 6.5 Hz,1H); 7.17-7.12 (m, 1H), 2.56 (s, 3H).

A slurry of 2-fluoro-3-iodo-4-methylbenzonitrile (2, 18.5 g, 70.7 mmol)in 75% sulfuric acid (29 mL) was stirred at 150° C. for 2 hours. Aftercooling, the mixture was poured over ice/water (275 g), the precipitatedsolid was filtered off, washed with water and dried to yield2-fluoro-3-iodo-4-methylbenzoic acid (3) as a creamy solid.

Yield: 19.18 g (97%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 13.30 (s, 1H); 7.75 (t, J=7.8Hz, 1H); 7.27 (d, J=8.0 Hz, 1H); 2.47 (s, 3H).

Acetyl chloride (4.90 mL, 68.7 mmol) was drop-wise added to a stirredsuspension of 2-fluoro-3-iodo-4-methylbenzoic acid (3, 19.1 g, 68.3mmol) in dry methanol (75 mL) at 0° C. The mixture was refluxed for 9hours. The volatiles were removed by evaporation under reduced pressureand the residue was treated with ethyl acetate (100 mL) and saturatedaqueous solution of sodium bicarbonate (100 mL). The mixture wasfiltered through a cotton plug (200 ml ethyl acetate washing). Phaseswere separated and the organic phase was dried over anhydrous magnesiumsulfate and evaporated. The residue was crystallized fromisopropanol/water (1:1, 30 mL) to furnish methyl2-fluoro-3-iodo-4-methylbenzoate (4) as an off-white needles.

Yield: 18.36 g (91%).

R_(F) (SiO₂, cyclohexane/diethyl ether 9:1): 0.50

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.80 (t, J=7.7 Hz, 1H); 7.10(d, J=8.0 Hz, 1H); 3.93 (s, 3H); 2.52 (s, 3H).

Solution of 2-fluoro-3-iodo-4-methylbenzoate (4, 18.5 g, 62.9 mmol),bis(pinacolato)diboron (5, 24.0 g, 94.4 mmol), anhydrous potassiumacetate (18.5 g, 189 mmol) and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) complex withdichloromethane (1.02 g, 1.25 mmol) in anhydrous dimethylsulfoxide (250mL) was stirred at 110° C. under argon atmosphere for 20 hours. Then thereaction mixture was cooled to ambient temperature, diluted with water(2000 mL) and extracted with ethyl acetate (4×500 mL). Organic layer wasseparated, dried over anhydrous sodium sulfate, filtered andconcentrated under reduced pressure. Crude product was purified by flashchromatography (Silicagel 60, 0.063-0.200 mm; eluent:cyclohexane/dichloromethane 9:1) to provide methyl2-fluoro-4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(6).

Yield: 13.0 g (70%).

R_(F) (SiO₂, cyclohexane/dichloromethane 9:1): 0.30

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.84 (t, J=8.0 Hz, 1H); 7.00(d, J=8.1 Hz, 1H); 3.90 (s, 3H); 2.47 (s, 3H); 1.39 (s, 12H).

Solution of methyl2-fluoro-4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(6, 11.7 g, 39.8 mmol), 1-bromopyrrolidine-2,5-dione (NBS, 9.20 g, 51.7mmol) and 2,2′-azobis(2-methylpropionitrile) (AIBN, 0.33 g, 1.99 mmol)in benzotrifluoride (170 mL) was stirred at 85° C. for 16 hours. Thereaction mixture was cooled to ambient temperature and 12% aqueoussolution of potassium hydroxide (80 mL) was added and the reactionmixture was stirred for 2 hours at room temperature. Aqueous layer wasseparated and another portion of 12% aqueous solution of potassiumhydroxide (50 mL) was added to the organic layer and the reactionmixture was stirred for another 30 minutes at room temperature. Combinedaqueous layers were then acidified with 1 M aqueous solution ofhydrochloric acid to pH<1 and allowed to stir at ambient temperature for20 hours. Precipitate was filtered to provide7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid(7) as beige solid.

Yield: 5.34 g (68%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.39 (s, 1H); 7.97 (t, J=7.3Hz, 1H); 7.32 (d, J=7.9 Hz, 1H); 5.04 (s, 2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 3.95 min.

LC-MS m/z: 373.4 (M+H)⁺.

1-Hydroxy-2,5-pyrrolidinedione (HOSu, 1.17 g, 10.2 mmol) and3-(ethyliminomethyleneamino)-N,N-dimethylpropan-1-amine hydrochloride(EDC.HCl, 1.95 g, 10.2 mmol) were added to a solution of7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid(7, 2.00 g, 10.2 mmol) in mixture oftetrahydrofuran/N,N-dimethylformamide (5:1, 50 mL) at room temperature.Reaction mixture was allowed to stir at ambient temperature for 2 hours.Volatiles were then evaporated, the residue was dissolved in ethylacetate (200 mL) and extracted with 1 M aqueous solution of hydrochloricacid (2×80 mL) and brine (1×50 mL). Organic layer was separated, driedover anhydrous sodium sulfate, filtered and concentrated under reducedpressure. Crude product was recrystallized from hot 2-propanol (50 mL)to provide 2,5-dioxopyrrolidin-1-yl7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (8)as pale yellow solid.

Yield: 1.30 mg (44%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.56 (s, 1H); 8.15 (dd, J=7.9and 6.6 Hz, 1H); 7.50 (d, J=8.1 Hz, 1H); 5.12 (s, 2H); 2.84 (s, 4H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.20 min.

LC-MS m/z: 294.4 (M+H)⁺.

Solution of 2,5-dioxopyrrolidin-1-yl7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (8,200 mg, 0.68 mmol), 3,5-bis(aminomethyl)benzoic acid dihydrochloride (9,86.0 mg, 0.34 mmol) and N,N-diisopropylethylamine (0.36 mL) in mixtureof N,N-dimethylformamide/water (4:1, 10 mL) was allowed to stir atambient temperature for 20 hours. Reaction mixture was then evaporatedand the rest was precipitated with 20% aqueous acetonitrile (15 mL).Resulting suspension was diluted with additional portion of water (20mL) and centrifuged. Solids were then collected and purified bypreparative LC/MS (SunFire Prep C18, 5 μm, 19×100 mm, acetonitrile/water5:95 to 100:0+0.1% FA) and freeze-dried to afford3,5-bis((7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)methyl)benzoicacid (10) as white solid.

Yield: 71.0 mg (39%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.38 (s, 2H); 8.99-8.87 (m,2H); 7.83 (s, 2H); 7.76 (t, J=7.3 Hz, 2H); 7.55 (s, 1H); 7.30 (d, J=7.9Hz, 2H); 5.03 (s, 4H); 4.52 (d, J=5.7 Hz, 4H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.16 min.

LC-MS m/z: 537.7 (M+H)⁺.

Example 7N-(5-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine

N-(5-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycinewas synthesized according to the reaction scheme shown in Chem. 7 andfollowing the procedure described below.

Solution of5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid(1, 140 mg, 0.71 mmol),1-((dimethylamino)(dimethyliminio)methyl)-1H-[1,2,3]triazolo[4,5-b]pyridine3-oxide hexafluorophosphate(V) (HATU, 265 mg, 0.70 mmol) andN,N-diisopropylethylamine (0.31 mL, 1.79 mmol) in dichloromethane (5 mL)was allowed to stir at ambient temperature. After 5 minutes, tert-butyl(2-aminoethyl)glycinate hydrochloride (2, 0.09 g, 0.36 mmol) was addedto the reaction mixture at room temperature and the reaction was stirredfor 18 hours. Volatiles were then evaporated under reduced pressure andconcentrated hydrochloric acid (2 mL) was added. Reaction mixture wasallowed to stir at room temperature for 2 hours. Then saturated aqueoussolution of sodium bicarbonate was added to adjust neutral pH. Aqueouslayer was extracted with acetonitrile (3×10 mL) and ethyl acetate (2×10mL). Organic solutions were then evaporated under reduced pressure. Thecrude product 3 was purified by preparative LC/MS (SunFire Prep C18, 5μm, 19×100 mm, acetonitrile/water 5:95 to 100:0+0.1% FA) with nosuccess. Isolated compound 3 was then purified by preparative HPLC(Column X-Select, C18, 15 μm; 30×150 mm; acetonitrile/water 3:97 to30:70+0.05% AA) and freeze-dried to affordN-(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine(3) as white solid.

Yield: 10 mg (6%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.39-9.23 (m, 2H); 8.55-8.22(m, 1H); 8.05-7.93 (m, 1H); 7.67-7.63 (m, 1H); 7.36-7.21 (m, 2H);5.00-4.97 (m, 4H); 4.20 (s, 1H); 3.88 (s, 1H); 3.70-3.65 (m, 2H);3.57-3.53 (m, 2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 2.98 min.

LC-MS m/z: 475.5 (M+H)⁺.

Example 8N-(4-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine

N-(4-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycinewas synthesized according to the reaction schemes shown in Chem. 8 andChem. 9 and following the procedure described below.

Intensively stirred solution of 3-fluoro-4-methylbenzoic acid (1, 61.7g, 400 mmol) in sulfuric acid (96%, 400 mL) was cooled by external icewater bath and N-bromosuccinimide (72.0 g, 405 mmol) was added in threeportions during 20 minutes. The mixture was stirred at room temperaturefor 4 hours then another portion of N-bromosuccinimide (72.0 g, 405mmol) was added at once and the whole mixture was stirred at roomtemperature overnight. Resulting suspension was diluted with ice water(3.00 L) and stirred for 10 minutes. The solid was filtered off, washedwith water (200 mL), triturated with water (3×600 mL) and sucked off asmuch as possible. Wet solid was suspended in water (400 mL), stirred atroom temperature and solution of sodium hydroxide (50.0 g, 1.25 mol in200 mL water) was added. Resulting solution was heated to 40° C.overnight. Filtration of slightly cloudy solution afforded clearyellowish filtrate to which solution of potassium bisulfate (180 g, 1.32mol in 400 mL water) was added. White precipitate was extracted with amixture of dichloromethane/tetrahydrofuran 4:1 (2×500 mL). Organicextracts were dried over anhydrous sodium sulfate and evaporated todryness to give white solid residue. Thionyl chloride (30.0 mL, 413mmol) was added to stirred cooled (−78° C.) suspension of this residuein anhydrous methanol (500 mL). Reaction mixture was allowed to warm toroom temperature and then heated to 60° C. overnight. The solution wascooled to room temperature and kept 4° C. overnight. Crystallinematerial was filtered off washed by methanol (2×50 mL), tert-butylmethyl ether (2×50 mL) and dried in vacuo to afford methyl2,3-dibromo-5-fluoro-4-methylbenzoate (2) as colorless crystals.

Yield: 78.2 g (60%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.37 (d, J=9.0 Hz, 1H); 3.94(s, 3H); 2.46 (d, J=2.3 Hz, 3H).

LC-MS purity: 98% (UV).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 40:60 to100:0+0.1% FA): 4.55 min.

LC-MS m/z: 327.2 (M+H)⁺.

A suspension of fine powdered copper (44.0 g, 692 mmol) and methyl2,3-dibromo-5-fluoro-4-methylbenzoate (2, 75.2 g, 231 mmol) in propionicacid (100 mL) was stirred and heated at 85-90° C. for 6 hours, cooled toroom temperature and diluted with mixture of cyclohexane/toluene (3:1,800 mL). Reaction mixture was washed with water (3×200 mL), 10% aqueoussolution of potassium bisulfate (2×200 mL) and brine (2×300 mL). Organicsolution was dried over anhydrous sodium sulfate and evaporated todryness to give yellowish oil which was purified by flash columnchromatography (Silicagel 60, 0.040-0.060 mm; eluent:cyclohexane/toluene 3:1) to afford methyl3-bromo-5-fluoro-4-methylbenzoate (3) as colorless crystals.

Yield: 52.5 g (92%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.51 (s, 1H); 7.37 (d, J=9.0Hz, 1H); 3.86 (s, 3H); 2.37 (d, J=2.4 Hz, 3H).

LC-MS purity: 99% (UV).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 40:60 to100:0+0.1% FA): 3.72 min.

LC-MS m/z: 347.3 (M+H)⁺.

Methyl 3-bromo-5-fluoro-4-methylbenzoate (3, 51.9 g, 210 mmol) wasdissolved in anhydrous 1,4-dioxane (400 mL), anhydrous potassium acetate(65.3 g, 666 mmol) and bis(pinacolato)diboron (4, 75.1 g, 296 mmol) wasadded at room temperature and this mixture was degassed.1,1′-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (1.88 g, 2.57mmol) was added and the mixture was heated to 75° C. in an argonatmosphere for 40 hours. The mixture was concentrated under reducedpressure and dissolved in toluene (1.1 L) and extracted with water(2×200 mL). Organic solution was dried using anhydrous sodium sulfate,evaporated under reduced pressure and then purified by flash columnchromatography (Silicagel 60, 0.040-0.063 mm; eluent: toluene/ethylacetate 9:1) to afford methyl3-fluoro-4-methyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(5) as white solid.

Yield: 50.0 g (81%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.20 (s, 1H); 7.70 (d, J=10.0Hz, 1H); 3.85 (s, 3H); 2.50 (s, 3H); 1.36 (s, 12H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 40:60 to100:0+0.1% FA): 6.12 min.

LC-MS m/z: 295.4 (M+H)⁺.

Azobisisobutyronitrile (AIBN, 0.86 g, 5.20 mmol) and N-bromosuccinimide(NBS, 25.4 g, 143 mmol) were added to a solution of methyl3-fluoro-4-methyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(5, 40.0 g, 136 mmol) in 1,2-dichloroethane (200 mL). The mixture wasrefluxed overnight. Reaction mixture was cooled to room temperature,diluted with dichloromethane (500 mL) and extracted with water (2×500mL). Organic solution was dried over anhydrous magnesium sulfate andevaporated to dryness to give methyl4-(bromomethyl)-3-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(6) as yellowish crystals. The product was used in the next step withoutfurther purification.

Yield: 35.5 g (70%).

LC-MS purity: 96% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 40:60 to100:0+0.1% FA): 6.53 min.

LC-MS m/z: 373.4 (M+H)⁺.

Methyl4-(bromomethyl)-3-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(6, 7.46 g, 20.0 mmol) stirred with 2.5 M aqueous solution of sodiumhydroxide (40.0 mL, 100 mmol) at room temperature overnight. 6 M aqueoussolution of hydrochloric acid (20.0 mL, 120 mmol) was added and themixture was stirred for 30 minutes and kept 4° C. overnight. Whiteprecipitate was collected by filtration and washed with water (2×100 mL)and air dried to afford4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid(7) as a white solid which was used in the next step without furtherpurification.

Yield: 3.76 g (96%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.8 (s, 1H); 9.57 (s, 1H);8.20 (s, 1H); 7.72 (d, J=7.1 Hz, 1H); 5.14 (s, 2H).

LC-MS purity: 95% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.22 min.

LC-MS m/z: 197.4 (M+H)⁺.

4-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid(1, 0.30 g, 1.53 mmol) was dissolved in acetonitrile (5 mL).2,3,4,5,6-Pentafluorophenol (0.28 g, 1.53 mmol) andN,N-dicyclohexylcarbodiimide (0.32 g, 1.53 mmol) were added at roomtemperature. After stirring for 16 hours, precipitate was filtered offand filtrate was evaporated under reduced pressure to giveperfluorophenyl4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (2)as a white solid.

Yield: 0.41 g (74%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.72 (s, 1H); 8.46 (s, 1H);8.05 (d, J=8.1 Hz, 1H); 5.23 (s, 2H).

(2-Aminoethyl)glycine (3, 0.06 g, 0.50 mmol) was dissolved inN,N-dimethylformamide (3 mL), triethylamine (0.42 mL, 3.00 mmol) andperfluorophenyl4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (2,0.40 g, 1.00 mmol) were added at room temperature. After stirring for 16hours at room temperature, all volatiles were then evaporated underreduced pressure and the residue was precipitated from ethyl acetate (40mL) and purified by preparative HPLC (SunFire Prep C18, 5 μm, 19×100 mm,acetonitrile/water 5:95 to 100:0+0.1% FA) and freeze-dried to affordN-(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine(4) as white solid.

Yield: 47.0 mg (20%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.83 (bs, 1H); 9.63-9.41 (m,2H); 8.78-8.52 (m, 1H); 8.13-7.92 (m, 1H); 7.79-7.45 (m, 2H); 7.22-6.99(m, 1H); 5.19-5.01 (m, 4H); 4.20 (s, 1H); 4.00 (s, 1H); 3.71-3.36 (m,4H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.19 min.

LC-MS m/z: 475.3 (M+H)⁺.

Example 9N-(6-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-N-(2-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxamido)ethyl)glycine

N-(6-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-N-(2-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxamido)ethyl)glycinewas synthesized according to the reaction scheme shown in Chem. 10 andfollowing the procedure described below.

6-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxylic acid(2, 0.25 g, 1.27 mmol) was dissolved in N,N-dimethylformamide (15 mL)and1-((dimethylamino)(dimethyliminio)methyl)-1H-[1,2,3]triazolo[4,5-b]pyridine3-oxide hexafluorophosphate (HATU, 0.49 g, 1.27 mmol) andN,N-diisopropylethylamine (0.89 mL, 5.10 mmol) were added. After 5minutes, tert-butyl (2-aminoethyl)glycinate hydrochloride (1, 0.13 g,0.64 mmol) was added to the reaction mixture at room temperature and thereaction was stirred for 3 days. Volatiles were then evaporated underreduced pressure and the ester 3 was used for the next step withoutfurther purification.

LC-MS purity: 66% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.55 min.

LC-MS m/z: 531.5 (M+H)⁺.

tert-ButylN-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-N-(2-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxamido)ethyl)glycinate(3, <0.64 mmol) was dissolved in 3.5 M solution of hydrogen chloride in1,4-dioxane (20 mL) and the mixture was stirred for 3 hours at roomtemperature. Volatiles were then evaporated under reduced pressure andthe residue was purified by preparative HPLC (Column X-Select, C18, 15μm; 30×150 mm; acetonitrile/water 3:97 to 30:70+0.05% AA) andfreeze-dried to affordN-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-N-(2-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxamido)ethyl)glycine4 as white solid.

Yield: 0.04 g (14%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.53-9.40 (m, 2H); 8.55-8.23(m, 1H); 7.67-7.40 (m, 3H); 7.36-7.22 (m, 1H); 5.04-4.94 (m, 3H); 4.76(bs, 1H); 4.22 (s, 1H); 3.97 (s, 1H); 3.73-3.64 (m, 2H); 3.58-3.52 (m,2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 2.97 min.

LC-MS m/z: 475.4 (M+H)⁺.

Example 10N²,N⁶-Bis(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysine

N²,N⁶-Bis(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysinewas synthesized according to the reaction scheme shown in Chem. 11 andfollowing the procedure described below.

L-Lysine hydrochloride (1, 68.0 mg, 0.38 mmol) was dissolved inN,N-dimethylformamide (6 mL) and water (3 mL). N,N-Diisopropylethylamine(0.39 mL, 2.25 mmol) and 2,5-dioxopyrrolidin-1-yl6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxylate (2,0.22 g, 0.75 mmol) were added at room temperature. After stirring for 3hours, volatiles were evaporated under reduced pressure and the residuewas purified by preparative HPLC (Column X-Bridge, C18, 15 μm; 30×150mm, acetonitrile/water 3:97 to 30:70+0.05% AA) and freeze-dried toaffordN²,N⁶-bis(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysine(3) as a white solid.

Yield: 89.0 mg (47%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.65 (bs, 1H); 9.41 (d,J=5.9 Hz, 2H); 8.60 (d, J=1.5 Hz, 1H); 8.39 (t, J=5.3 Hz, 1H); 7.62-7.53(m, 2H); 7.53-7.43 (m, 2H); 4.97 (d, J=5.5 Hz, 4H); 4.41-4.29 (m, 1H);3.30-3.20 (m, 2H); 1.88-1.68 (m, 2H); 1.60-1.37 (m, 4H).

LC-MS purity: 97% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.08 min.

LC-MS m/z: 503.5 (M+H)⁺.

Example 113-Borono-5-((3-borono-4-fluorophenyl)sulfonyl)-4-fluorobenzoic acid

3-Borono-5-((3-borono-4-fluorophenyl)sulfonyl)-4-fluorobenzoic acid wassynthesized according to the reaction scheme shown in Chem. 12 andfollowing the procedure described below.

3-Bromo-4-fluorobenzaldehyde (1, 4.06 g, 20.0 mmol) and periodic acid(5.02 g, 22.0 mmol) were suspended in acetonitrile (100 mL) andpyridinium chlorochromate (PCC, 86.0 mg, 0.40 mmol) was added withstirring. The resulting viscous suspension was stirred for two hours andthen concentrated to half its volume. Water (300 mL) was added withstirring, resulting in the precipitation of a white solid, which wascollected by filtration, washed with water (2×50 mL) and air dried togive 3-bromo-4-fluorobenzoic acid (2).

Yield: 3.85 g (88%).

3-Bromo-4-fluorobenzoic acid (2, 2.19 g, 10.0 mmol) was dissolved insulfuric acid (25 mL) and N-iodosuccinimide (NIS, 2.47 g, 3.00 mmol) wasadded in portions with stirring. The reaction mixture was then stirredfor an hour and then it was poured into ice-cold water (150 mL) toprecipitate the product, which was washed with water (2×20 mL) and airdried. The crude acid was recrystallized from toluene to give the titlecompound 3-bromo-4-fluoro-5-iodobenzoic acid (3) as off-white solid.

Yield: 2.46 g (81%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 9.60 (bs, 1H); 8.30 (s, 1H);8.13 (s, 1H).

3-Bromo-4-fluoro-5-iodobenzoic acid (3, 1.72 g, 5.00 mmol) was dissolvedin dry tetrahydrofuran (15 mL) and cooled to 0° C. in an ice-bath. Neatborane-dimethyl sulfide (1.00 ml, 10.0 mmol) was added (gas evolution)and the resulting mixture was stirred for 16 hours (overnight). Thereaction mixture was carefully quenched with methanol (2 mL), evaporatedto dryness and the residue was co-distilled with methanol (2×10 mL). Theresulting solid was triturated with n-hexane and filtered to give the(3-bromo-4-fluoro-5-iodophenyl)methanol (4) as white solid.

Yield: 1.48 g (90%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.74-7.66 (i, 1H); 7.58-7.50(m, 1H); 4.64 (s, 2H); 1.87 (bs, 1H).

(3-Bromo-4-fluoro-5-iodophenyl)methanol (4, 825 mg, 2.50 mmol),anhydrous potassium carbonate (690 mg, 5.00 mmol), copper iodide (95.0mg, 0.50 mmol) and 3-bromo-4-fluorobenzenethiol (5, 776 mg, 3.75 mmol)were suspended in dry 1,2-dimethoxyethane (10 mL) and the resultingsuspension was stirred for 48 hours at 80° C. After cooling to ambienttemperature, the reaction mixture was diluted with ethyl acetate (20mL), filtered through Celite (washed with ethyl acetate) and evaporated.The residue was purified by flash chromatography (Silicagel 60,0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 3:1) to give 6 ascolorless oil. It was dissolved in methanol (10 mL) and water (5 mL) andpotassium peroxymonosulfate (2.30 g, 3.75 mmol) was added in portions.After stirring for 16 hours, the reaction mixture was taken up in ethylacetate (50 mL) and washed with water (30 mL) and brine (30 mL). Afterdrying the organic layer with anhydrous sodium sulfate, filtration andevaporation. The crude product was purified by flash chromatography(Silicagel 60, 0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 3:1 to1:1) to give(3-bromo-5-((3-bromo-4-fluorophenyl)sulfonyl)-4-fluorophenyl) methanol(7) as colorless solid.

Yield: 663 mg (60%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.26-8.19 (i, 1H); 8.05-7.97(m, 2H); 7.89-7.83 (m, 1H); 7.36-7.26 (m, 1H, overlapping with CHCl₃);4.79 (s, 2H); 2.18 (bs, 1H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 50:50 to100:0+0.1% FA): 2.14 min.

LC-MS m/z: 443.2 (M+H)⁺.

(3-bromo-5-((3-bromo-4-fluorophenyl)sulfonyl)-4-fluorophenyl)methanol(7, 621 mg, 1.405 mmol) and periodic acid (707 mg, 3.1 mmol) weresuspended in acetonitrile (10 mL) and pyridinium chlorochromate (PCC, 15mg, 0.07 mmol) was added with stirring. The resulting viscous suspensionwas stirred for 16 hours and then mixture was taken up in ethyl acetate(30 mL) and washed with water (30 mL) and brine (30 mL). The organiclayer dried with anhydrous sodium sulfate, filtered and evaporated togive pure 3-bromo-5-((3-bromo-4-fluorophenyl)sulfonyl)-4-fluorobenzoicacid (8) as colorless solid.

Yield: 620 mg (97%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.52-8.46 (m, 1H); 8.33-8.26(m, 1H); 8.07-8.00 (m, 1H), 7.86-7.79 (m, 1H), 7.22-7.13 (s, 1H); 4.24(bs, 1H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 50:50 to100:0+0.1% FA): 2.66 min.

LC-MS m/z: 457.8 (M+H)⁺.

A 25 mL reaction vessel was charged with potassium acetate (392 mg, 4.00mmol) and the salt was dried for 1 hour at 110° C. in vacuo. Aftercooling to room temperature, the reaction vessel was backfilled withnitrogen and charged3-bromo-5-((3-bromo-4-fluorophenyl)sulfonyl)-4-fluorobenzoic acid (8,364 mg, 0.80 mmol), palladium acetate (9.0 mg, 0.04 mmol),2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos, 38.0 mg,0.08 mmol) and bis(pinacolato)diboron (447 mg, 1.76 mmol). The reactionvessel was then evacuated and backfilled with nitrogen (this procedurewas repeated twice), anhydrous tetrahydrofuran (4 mL) was added withsyringe, the vessel was sealed with rubber septum and submerged in theheating bath preheated to 60° C. After stirring at 400 rpm for 20 hours(overnight) the reaction mixture was diluted with dichloromethane (15mL) and quickly filtered through a short plug of Celite (3.00 g) withthe aid of more dichloromethane (3×5 mL). The filtrate was concentratedunder reduced pressure to afford the crude4-fluoro-3-((4-fluoro-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)sulfonyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoicacid (9) a beige foam. A part of this material was purified (pinacolester hydrolysis occurred spontaneously) by preparative LC-MS (SunFirePrep C18, 5 μm, 19×100 mm, acetonitrile/water 5:95 to 100:0+0.1% FA).The fractions were pooled and freeze-dried to give3-borono-5-((3-borono-4-fluorophenyl) sulfonyl)-4-fluorobenzoic acid(10) as white solid.

Yield: 34 mg (11%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂O, 10:1, δ_(H)): 8.70-8.64 (m,1H); 8.59-8.53 (m, 1H); 8.35-8.28 (m, 1H), 8.14-8.05 (m, 1H), 7.38-7.28(s, 1H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 3.28 min.

LC-MS m/z: 387.4 (M+H)⁺.

Example 12 3-Borono-5-(3-borono-5-fluorobenzoyl)benzoic acid

3-Borono-5-(3-borono-5-fluorobenzoyl)benzoic acid was synthesizedaccording to the reaction scheme shown in Chem. 13 and following theprocedure described below.

3-Bromo-5-iodobenzoic acid (1, 6.52 g, 20.0 mmol) was suspended inmethanol (40 mL) and methanesulfonic acid (0.4 mL) was added. Theresulting mixture was stirred for 16 hours at 60° C. (oil bath). Theresulting clear solution was cooled to −20° C. in the freezer for 16hours and the resulting solid was collected by filtration, washed withchilled (−20° C.) methanol and dried in vacuo to give methyl3-bromo-5-iodobenzoate (2) as an off-white solid.

Yield: 4.70 g (69%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.30 (s, 1H); 8.14 (s, 1H);8.04 (s, 1H); 3.93 (s, 1H).

1,3-Dibromo-5-fluorobenzene (3, 0.63 mL, 5.00 mmol) was dissolved in drydiethyl ether (15 mL) and cooled down to −78° C. 2.35 M n-Butyllithiumin hexane (2.20 mL, 2.35 M in hexane, 5.25 mmol) was added drop-wisewith stirring. After 15 minutes, dry N,N-dimethylformamide (0.77 mL,10.0 mmol) was added and the resulting mixture was stirred at for 15minutes and then allowed to warm to ambient temperature. After one hour,the reaction mixture was quenched with 1 M aqueous solution ofhydrochloric acid (15 mL). Layers were separated and the organic layerwas washed with brine (15 mL), dried over anhydrous magnesium sulfateand evaporated to give 3-bromo-5-fluorobenzaldehyde (4) as yellowish oilwhich solidified on storage in freezer.

Yield: 1.02 g (100%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 9.92 (s, 1H); 7.80 (bs, 1H);7.50 (bs, 2H).

Methyl 3-bromo-5-iodobenzoate (2, 341 mg, 1.00 mmol) was dissolved indry tetrahydrofuran (4 mL) under nitrogen atmosphere and cooled down to−40° C. 1.3 M Isopropylmagnesium chloride-lithium chloride complex intetrahydrofuran (0.80 mL, 1.05 mmol) was added slowly drop-wise. After30 minutes 3-bromo-5-fluorobenzaldehyde (4, 243 mg, 1.20 mmol) was addedwith the aid of dry tetrahydrofuran (0.5 mL). The resulting mixture wasallowed to warm to room temperature overnight (16 hours). The reactionwas quenched by addition of 0.5 M aqueous solution of hydrochloric acid(5 mL) and extracted with ethyl acetate (1×20 mL). Organic layer waswashed with brine (15 mL) and dried over anhydrous sodium sulfate,filtered and evaporated. The residue was purified by flash columnchromatography (Silicagel 60, 0.063-0.200 mm; eluent: cyclohexane/ethylacetate 10:1 to 6:1) to give methyl3-bromo-5-((3-bromo-5-fluorophenyl)(hydroxy)methyl)benzoate (5) as acolorless oil. It was dissolved in dry dichloromethane (5 mL) andpyridinium chlorochromate (PCC, 200 mg, 0.93 mmol) was added. Thereaction mixture was then stirred overnight (16 hours) before it wasquenched with 2-propanol (0.3 mL). After stirring for one hour at roomtemperature, the reaction mixture was filtered through a silica gel plug(5 g) topped with Celite S and washed with dichloromethane (2×10 mL).The solvent was removed in vacuo and the residue was purified by flashcolumn chromatography (Silicagel 60, 0.063-0.200 mm; eluent:cyclohexane/dichloromethane 6:1 to 2:1) to give methyl3-bromo-5-(3-bromo-5-fluorobenzoyl)benzoate (6) as colorless solid.

Yield: 208 mg (50%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.43 (s, 1H); 8.30 (s, 1H);8.11 (s, 1H); 7.71 (s, 1H); 7.53 (d, J=7.6 Hz, 1H); 7.41 (d, J=8.3 Hz,1H); 3.97 (s, 3H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 2.84 min.

LC-MS m/z: neither molecular oil nor fragments could be detected.

A 25 mL reaction vessel was charged with potassium acetate (188 mg, 1.92mmol) and the salt was dried for 1 hour at 110° C. in vacuo. Aftercooling to room temperature, the reaction vessel was backfilled withnitrogen and charged with methyl3-bromo-5-(3-bromo-5-fluorobenzoyl)benzoate (6, 200 mg, 0.48 mmol),palladium acetate (5.40 mg, 0.24 mmol),2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos, 23.0 mg,0.48 mmol) and bis(pinacolato)diboron (270 mg, 1.06 mmol). The reactionvessel was then evacuated and backfilled with nitrogen (this procedurewas repeated twice), anhydrous tetrahydrofuran (3 mL) was added withsyringe, the vessel was sealed with rubber septum and submerged in theheating bath preheated to 60° C. After stirring at 400 rpm for 16 hours(overnight) the reaction mixture was cooled to ambient temperature,diluted with cyclohexane (24 mL) and filtered through a short plug ofsilica (5 g) topped with Celite S with the aid of dichloromethane (3×10mL). The filtrate was concentrated under reduced pressure to afford themethyl3-(3-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(7) as yellowish waxy solid.

Yield: 245 mg (100%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.69 (s, 1H); 8.48 (s, 1H);8.38 (s, 1H); 7.97 (s, 1H); 7.72 (d, J=8.5 Hz, 1H); 7.54 (d, J=9.0 Hz,1H); 3.95 (s, 3H); 1.36 (s, 12H); 1.35 (s, 12H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 3.79 min.

LC-MS m/z: 511.6 (M+H)⁺.

Methyl3-(3-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(7, 245 mg, 0.48 mmol) was dissolved in acetonitrile (3 mL) and water(0.6 mL). Periodic acid (438 mg, 1.92 mmol) was added and the resultingmixture was vigorously stirred at ambient temperature for an hour. Thereaction mixture was taken up in ethyl acetate (20 mL) and washed withwater (20 mL) and brine (20 mL), dried over anhydrous sodium sulfate,filtered and evaporated. The residue was dissolved in methanol (3 mL)and water (0.3 mL) and potassium hydroxide (270 mg, 4.80 mmol) was addedin one portion. The reaction mixture was stirred for 48 hours, dilutedwith 1 M aqueous solution of potassium hydroxide (5 mL) and water (10mL) and washed with dichloromethane (2×7 mL). The aqueous phase wasacidified by the addition of concentrated hydrochloric acid (3 mL) andextracted with ethyl acetate (15 mL). The organic layer was washed withbrine (15 mL), dried over anhydrous sodium sulfate, filtered andevaporated. The crude product was dissolved in a minimum amount of wet(shaken thoroughly with water) 2-methyltetrahydrofuran and the solutionadded drop-wise to an ice-cold n-hexane (5 mL) with stirring, resultingin the precipitation of a product. The solid was collected by filtrationand washed with cyclohexane (2×5 mL) to give the title3-borono-5-(3-borono-5-fluorobenzoyl)benzoic acid (8) as off-whitesolid.

Yield: 133.0 mg (83%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂0; 10:1, δ_(H)): 8.75 (s, 1H);8.47-8.40 (m, 2H); 8.05 (s, 1H); 7.85-7.78 (m, 1H); 7.60-7.53 (m, 1H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 2.52 min.

LC-MS m/z: 333.4 (M+H)⁺.

Example 13 3-Borono-5-(5-borono-2,4-difluorobenzoyl)benzoic acid

3-Borono-5-(5-borono-2,4-difluorobenzoyl)benzoic acid was synthesizedaccording to the reaction schemes shown in Chem. 14 and Chem. 15 andfollowing the procedure described below.

1,5-Dibromo-2,4-difluorobenzene (1, 1.36 g, 5.00 mmol) was dissolved indry diethyl ether (15 mL) and cooled down to −78° C. 2.35 Mn-Butyllithium in hexane (2.20 mL, 5.25 mmol) was added drop-wise withstirring. After 15 minutes, dry N,N-dimethylformamide (0.77 mL, 10.0mmol) was added and the resulting mixture was stirred at for 15 minutesand then allowed to warm to ambient temperature. After one hour, thereaction mixture was quenched with 1.0 M aqueous solution ofhydrochloric acid (15 mL). Layers were separated and the organic layerwas washed with brine (15 mL), dried over anhydrous magnesium sulfateand evaporated. The residue was purified by flash column chromatography(Silicagel 60, 0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 20:1)5-bromo-2,4-difluorobenzaldehyde (2) as colorless oil which solidifiedon storage in freezer.

Yield: 780 mg (70%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 10.26 (s, 1H); 8.14 (dd, J=9.6and 8.0 Hz, 1H); 7.05 (d, J=8.0 Hz, 1H).

Methyl 3-bromo-5-iodobenzoate (3, 681 mg, 2.00 mmol) was dissolved indry tetrahydrofuran (4 mL) under nitrogen atmosphere and cooled down to−40° C. 1.3 M Isopropylmagnesium chloride-lithium chloride complex intetrahydrofuran (1.7 mL, 2.20 mmol) was added slowly drop-wise. After 30minutes 5-bromo-2,4-difluorobenzaldehyde (2, 530 mg, 2.40 mmol) wasadded with the aid of dry tetrahydrofuran (0.5 mL). The resultingmixture was allowed to warm to room temperature overnight (16 hours).The reaction was quenched by addition of 0.5 M aqueous solution ofhydrochloric acid (15 mL) and extracted with ethyl acetate (1×30 mL).Organic layer was washed with brine (20 mL) and dried over anhydroussodium sulfate, filtered and evaporated. The residue was purified byflash column chromatography (Silicagel 60, 0.063-0.200 mm; eluent:cyclohexane/ethyl acetate 8:1) to give methyl3-bromo-5-((5-bromo-2,4-difluorophenyl) (hydroxy)methyl)benzoate (4) asa colorless oil. It was dissolved in dry dichloromethane (7 mL) andpyridinium chlorochromate (PCC, 491 mg, 2.28 mmol) was added. Thereaction mixture was then stirred overnight (16 hours) before it wasquenched with 2-propanol (0.6 mL). After stirring for one hour at roomtemperature, the reaction mixture was filtered through a silica gel plug(10 g) topped with Celite S and washed with dichloromethane (2×20 mL).The solvent was removed in vacuo and the residue was purified by flashcolumn chromatography (Silicagel 60, 0.063-0.200 mm; eluent:cyclohexane/dichloromethane 6:1 to 2:1) to give methyl3-bromo-5-(5-bromo-2,4-difluorobenzoyl)benzoate (5) as colorless solid.

Yield: 606 mg (70%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.41 (s, 1H); 8.29 (d, J=1.6Hz, 1H); 8.12 (d, J=1.2 Hz, 1H); 7.87 (t, J=7.3 Hz, 1H); 7.04 (dd, J=9.3and 8.1 Hz, 1H); 3.96 (s, 3H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 2.76 min.

LC-MS m/z: 435.3 (M+H)⁺

A 25 mL reaction vessel was charged with potassium acetate (524 mg, 5.35mmol) and the salt was dried for 1 hour at 110° C. in vacuo. Aftercooling to room temperature, the reaction vessel was backfilled withnitrogen and charged with methyl methyl3-bromo-5-(5-bromo-2,4-difluorobenzoyl)benzoate (5, 581 mg, 1.34 mmol),palladium acetate (9.00 mg, 0.04 mmol),2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos, 38.0 mg,0.08 mmol) and bis(pinacolato)diboron (748 mg, 2.94 mmol). The reactionvessel was then evacuated and backfilled with nitrogen (this procedurewas repeated twice), anhydrous tetrahydrofuran (6 mL) was added withsyringe, the vessel was sealed with rubber septum and submerged in theheating bath preheated to 60° C. After stirring at 400 rpm for 16 hours(overnight) the reaction mixture was cooled to ambient temperature,diluted with cyclohexane (18 mL) and filtered through a short plug ofsilica (5.0 g) topped with Celite S with the aid of dichloromethane(3×10 mL). The filtrate was concentrated under reduced pressure toafford the methyl3-(2,4-difluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate (6) asyellowish waxy solid. It was dissolved in acetonitrile (8 mL) and water(2 mL). Periodic acid (1.22 g, 5.35 mmol) was added and the resultingmixture was vigorously stirred at ambient temperature for two hours. Thereaction mixture was taken up in ethyl acetate (30 mL) and washed withwater (20 mL) and brine (20 mL), dried over anhydrous sodium sulfate,filtered and evaporated. The crude product was dissolved in the minimumamount of wet ethyl acetate (shaken thoroughly with water) and thesolution added drop-wise to an ice-cold n-hexane (5 mL) with stirring,resulting in the precipitation of a product. The solid was collected byfiltration and washed with cold n-hexane (2×5 mL) to give the title(5-(3-borono-5-(methoxycarbonyl)benzoyl)-2,4-difluorophenyl)boronic acid(7) as off-white solid.

Yield: 443.0 mg (90%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂O 10:1, δ_(H)): 8.82-8.68 (m,1H); 8.46 (dd, J=16.8 and 1.4 Hz, 2H); 8.01 (dd, J=8.7 and 7.0 Hz, 1H);7.12 (dd, J=10.4 and 9.5 Hz, 1H); 3.91 (s, 3H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 3.99 min.

LC-MS m/z: 365.3 (M+H)⁺.

(5-(3-Borono-5-(methoxycarbonyl)benzoyl)-2,4-difluorophenyl)boronic acid(1, 200 mg, 548 μmol) was dissolved in methanol (2 mL) and water (0.7mL). Lithium hydroxide monohydrate (116 mg, 2.76 mmol) was added and theresulting mixture was vigorously stirred at ambient temperature for sixhours. The reaction mixture was taken up in ethyl acetate (15 mL) andwashed with 1 M aqueous solution of hydrochloric acid (15 mL) and brine(15 mL), dried over anhydrous sodium sulfate, filtered and evaporated.The crude product was dissolved in the minimum amount of wet ethylacetate (shaken thoroughly with water) and the solution added drop-wiseto an ice-cold n-hexane (5 mL) with stirring, resulting in theprecipitation of a product. The solid was collected by filtration andwashed with cold n-hexane (2×5 mL) to give the title3-borono-5-(5-borono-2,4-difluorobenzoyl)benzoic acid (2) as colorlesssolid.

Yield: 140 mg (73%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂O 10:1, δ_(H)): 8.77 (s, 1H);8.46 (dd, J=10.7 and 1.1 Hz, 2H); 8.00 (dd, J=8.7 and 7.0 Hz, 1H); 7.11(dd, J=10.4 and 9.5 Hz, 1H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.13 min.

LC-MS m/z: 351.3 (M+H)⁺.

Example 14N⁶-(4-Borono-2-fluorobenzoyl)-N²-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysine

N⁶-(4-Borono-2-fluorobenzoyl)-N²-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysinewas synthesized according to the reaction scheme shown in Chem. 16 andfollowing the procedure described below.

N_(a)-(tert-Butoxycarbonyl)-L-lysine (1, 75.0 mg, 0.31 mmol) wasdissolved in N,N-dimethylformamide (3 mL) and water (1 mL).N,N-Diisopropylethylamine (0.27 mL, 1.53 mmol) and2,5-dioxopyrrolidin-1-yl2-fluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate (2,0.20 g, 0.71 mmol) were added at room temperature. After stirring for 3hours, volatiles were evaporated under reduced pressure. The compound 3was dissolved in anhydrous 1,4-dioxane (2 mL) and 5.2 M solution ofhydrogen chloride in 1,4-dioxane was added (5 mL), then the reactionmixture was stirred at room temperature. After stirring for 1 hour,volatiles were evaporated under reduced pressure to give compound 4,which was re-dissolved in N,N-dimethyl formamide (3 mL) and water (1mL). N,N-Diisopropylethylamine (0.32 mL, 1.80 mmol) and2,5-dioxopyrrolidin-1-yl6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxylate (5,89.0 mg, 0.31 mmol) were added at room temperature. After stirring for 2hours, volatiles were evaporated under reduced pressure and the residuewas purified by preparative HPLC (SunFire Prep C18, 5 μm, 19×100 mm,acetonitrile/water 5:95 to 100:0+0.1% FA) and freeze-dried to affordN⁶-(4-borono-2-fluorobenzoyl)-N²-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysine(6) as a white solid.

Yield: 88.0 mg (62%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.43 (bs, 1H); 8.70 (bs, 1H);8.47 (d, J=6.4 Hz, 1H); 8.35-8.21 (m, 1H); 7.68-7.42 (m, 5H); 4.99 (s,2H); 4.39-4.24 (m, 1H); 3.28-3.18 (m, 2H); 1.93-1.66 (m, 2H); 1.62-1.33(m, 4H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.48 min.

LC-MS m/z: 491.5 (M+H)⁺.

Example 15(S)-2,3-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid

(S)-2,3-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid was synthesized according to the reaction scheme shown in Chem. 17and following the procedure described below.

(S)-2,3-Diaminopropanoic acid hydrochloride (1, 50.0 mg, 0.36 mmol) wasdissolved in N,N-dimethylformamide (2 mL) and water (1 mL).N,N-Diisopropylethylamine (0.37 mL, 2.13 mmol) and2,5-dioxopyrrolidin-1-yl7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (2,0.20 g, 0.71 mmol) were added at room temperature. After stirring for 2hours, volatiles were evaporated under reduced pressure and the residuewas washed with 1 M aqueous hydrochloric acid (3 mL). Precipitate wascollected and purified by preparative HPLC (SunFire Prep C18, 5 μm,19×100 mm, acetonitrile/water 5:95 to 100:0+0.1% FA) and freeze-dried toafford(S)-2,3-bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid (3) as a white solid.

Yield: 55.0 mg (34%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.90 (bs, 1H); 9.38 (d,J=8.8 Hz, 2H); 8.57-8.38 (m, 2H); 7.88-7.69 (m, 2H); 7.31 (t, J=7.4 Hz,2H); 5.03 (d, J=4.2 Hz, 4H); 4.72-4.59 (m, 1H); 3.82-3.65 (m, 2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 4.22 min.

LC-MS m/z: 461.5 (M+H)⁺.

Example 16(S)-2,3-Bis(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid

(S)-2,3-Bis(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid was synthesized according to the reaction schemes shown in Chem. 18and Chem. 19 and following the procedure described below.

1-Bromopyrrolidine-2,5-dione (NBS, 105 g, 584 mmol) was added to asolution of 2-fluoro-4-methylbenzoic acid (1, 90.0 g, 584 mol) inconcentrated sulfuric acid (1.1 L) and the reaction mixture was allowedto stir at ambient temperature for 16 hours. The reaction mixture wasthen poured into ice-water (5 L). Resulting precipitate was filteredoff, washed with water (1.5 L) and dissolved in ethyl acetate (1.2 L);dried over anhydrous sodium sulfate, filtered and evaporated to provide5-bromo-2-fluoro-4-methylbenzoic acid (2) as white solid.

Yield: 133.5 g (98%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.20 (d, J=6.9 Hz, 1H); 7.11(d, J=11.4 Hz, 1H); 2.47 (s, 3H).

Concentrated sulfuric acid (10 mL) was added to a solution of5-bromo-2-fluoro-4-methylbenzoic acid (2, 133 g, 570 mmol) in methanol(1 L) and the reaction mixture was allowed to stir under reflux for 4hours and at ambient temperature for 16 hours. The reaction mixture wasthen evaporated under reduced pressure, dissolved in diethyl ether (800mL), extracted with water (2×600 mL) and mixture of saturated solutionof potassium carbonate (300 mL) and brine (300 mL). Organic layer wasseparated, dried over anhydrous sodium sulfate, filtered and evaporatedto provide methyl 5-bromo-2-fluoro-4-methylbenzoate (3) as white solid.

Yield: 125 g (89%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.10 (d, J=6.6 Hz, 1H); 7.06(d, J=11.1 Hz, 1H); 3.92 (s, 3H); 2.43 (s, 3H).

The suspension of 1-bromopyrrolidine-2,5-dione (NBS, 131 g, 735 mmol)and 5-bromo-2-fluoro-4-methylbenzoate (3, 120 g, 490 mmol) in water (1L) was stirred for two days under 100 W light bulb at 70° C. If thereaction rate is slow, an extra 0.5 equivalent of NBS is added. Thesolution at 70° C. should stay clear to prevent the absorption of theradiation. Reaction mixture was extracted with diethyl ether (2×1).Organic layers were washed with brine (1 L). To reduce bromine sodiummetabisulfite pentahydrate was added to separatory funnel until thesolution discoloured. Organic layer was separated, dried over anhydroussodium sulfate, filtered and evaporated. The crude product was purifiedby flash chromatography (Silicagel, 0.063-0.200 mm; eluent:cyclohexane/ethyl acetate 15:1 to 9:1) to provide a mixture of methyl5-bromo-2-fluoro-4-(bromomethyl)benzoate (4) and a product of radicaldibromination. The mixture was diluted in dry tetrahydrofuran (600 mL),N,N-diisopropylethylamine (26.0 ml, 200 mmol) and diethylphosphite (35.0mL, 200 mmol) were added to the solution at 0° C. The reaction mixturewas then allowed to stir at ambient temperature for 18 hours. Thesolvent was evaporated and the crude product was dissolved in ethylacetate and washed with water (1 L) and 1 M hydrochloric acid (300 mL),brine (500 mL), 1 M aqueous solution of potassium hydrogen carbonate(500 mL). Organic layer was separated, dried over anhydrous sodiumsulfate, filtered and evaporated. The crude product was purified bycolumn chromatography (Silicagel, 0.063-0.200 mm; eluent:cyclohexane/ethyl acetate 9:1) to give methyl5-bromo-2-fluoro-4-(bromomethyl) benzoate (4).

Yield: 96 g (60%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 9:1): 0.50.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.16 (d, J=6.6 Hz, 1H); 7.31(d, J=10.2 Hz, 1H); 4.54 (s, 2H); 3.95 (s, 3H).

Solution of methyl 5-bromo-2-fluoro-4-(bromomethyl)benzoate (4, 96.0 g,290 mmol) and potassium acetate (59.0 g, 601 mmol) in acetonitrile (1 L)was stirred at 75° C. overnight. The suspension was filtered throughcotton-wool and evaporated. The crude product was dissolved indichloromethane and filtered again. Purification by columnchromatography (Silicagel, 0.063-0.200 mm; eluent: cyclohexane/ethylacetate 9:1 to 1:1) provided methyl5-bromo-2-fluoro-4-(acetylmethyl)benzoate (5).

Yield: 70 g (80%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 9:1): 0.30.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.15 (d, J=6.3 Hz, 1H); 7.24(d, J=11.1 Hz, 1H); 5.18 (s, 2H); 3.95 (s, 3H); 2.21 (s, 3H).

Solution of methyl 5-bromo-2-fluoro-4-(acetylmethyl)benzoate (5, 70.0 g,230 mmol), bis(pinacolato)diboron (6, 64.3 g, 253 mmol), potassiumacetate (67.6 g, 690 mmol) and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (3.00 g,4.00 mmol) in dry 1,4-dioxane (600 mL) was allowed to stir at 80° C.under argon atmosphere for 24 hours. Then the reaction mixture wascooled to ambient temperature, filtered and evaporated. The crudeproduct was filtered through silica gel (Silicagel, 0.063-0.200 mm;eluent: cyclohexane/ethyl acetate 9:1 to 4:1) to provide methyl2-fluoro-4-(acetylmethyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(7).

Yield: 76.2 g (94%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 9:1): 0.30.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.42 (d, J=8.4 Hz, 1H); 7.19(d, J=12 Hz, 1H); 5.42 (s, 2H); 3.94 (s, 3H); 2.16 (s, 3H); 1.35 (s,12H).

Solution of methyl2-fluoro-4-(acetylmethyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(7, 76.2 g, 216 mmol) and sodium hydroxide (43.0 g, 1.08 mol) in water(700 mL) was stirred at ambient temperature for 3 hours. Then solutionof hydrochloric acid (35%, 120 mL) in water (200 mL) was added to lowerthe pH to 1. The reaction mixture was put into the fridge for 16 hours.Precipitate was filtered and freeze dried to provide5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid(8) as white solid.

Yield: 40.7 g (96%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 13.17 (bs, 1H); 9.38 (bs,1H); 8.29 (d, J=7.7 Hz, 1H); 7.36 (d, J=11.2 Hz, 1H); 5.02 (s, 2H).

LC-MS purity: 98% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 4.18 min.

LC-MS m/z: 197.3 (M+H)⁺.

Solution of 2,3,4,5,6-pentafluorophenol (939 mg, 5.10 mmol),5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid(1, 1.00 g, 5.10 mmol) and N,N′-dicyclohexylcarbodiimide (DCC, 1.05 g,5.10 mmol) in acetonitrile (30 mL) was stirred at ambient temperatureovernight. The reaction mixture was filtered, washed with acetonitrileand evaporated. Crude product 2 (618 mg, 1.71 mmol) reacted with2,3-diaminopropionic acid hydrochloride (120 mg, 854 μmol) inN,N-dimethylformamide (12 mL) and water (6 mL) at ambient temperatureovernight. Crude product 3 was purified by preparative HPLC (SunFirePrep C18, 5 μm, 19×100 mm, acetonitrile/water 20:80 to 100:0+0.1% FA)and freeze-dried to afford(S)-2,3-bis(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid (3) as a white solid.

Yield: 54.0 mg (14%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.88 (bs, 1H); 9.37 (d,J=5.9 Hz, 2H); 8.55 (dd, J=7.3 and 3.4 Hz, 1H); 8.50-8.38 (m, 1H); 8.09(d, J=7.5 Hz, 1H); 8.02 (d, J=7.5 Hz, 1H); 7.36 (dd, J=10.8 Hz and 8.3Hz, 2H); 5.01 (d, J=4.2 Hz, 4H); 4.70-4.59 (m, 1H); 3.84-3.65 (m, 2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 4.43 min.

LC-MS m/z: 461.4 (M+H)⁺.

Example 17(S)-2,3-Bis(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoic acid

(S)-2,3-Bis(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoic acid was synthesized according to the reaction scheme shown inChem. 20 and following the procedure described below.

(S)-2,3-Diaminopropanoic acid hydrochloride (1, 72.0 mg, 0.36 mmol) wasdissolved in N,N-dimethylformamide (6 mL) and water (2 mL).N,N-Diisopropylethylamine (0.54 mL, 3.07 mmol) and2,5-dioxopyrrolidin-1-yl4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (2,0.30 g, 1.02 mmol) were added at room temperature. After stirring for 2hours, volatiles were evaporated under reduced pressure and the residuewas purified by preparative HPLC (SunFire Prep C18, 5 μm, 19×100 mm,acetonitrile/water 5:95 to 100:0+0.1% FA) and freeze-dried to afford(S)-2,3-bis(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid (3) as a white solid.

Yield: 95.0 mg (40%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.55 (d, J=6.2 Hz, 2H); 8.85(d, J=7.5 Hz, 1H); 8.78 (t, J=5.5 Hz, 1H); 8.07 (d, J=16.7 Hz, 2H);7.79-7.62 (m, 2H); 5.13 (d, J=6.1 Hz, 4H); 4.75-4.60 (m, 1H); 3.90-3.64(m, 2H).

LC-MS purity: 97% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.30 min.

LC-MS m/z: 461.4 (M+H)⁺.

Example 18(3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)difluoromethyl)benzoyl)glycine

(3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)difluoromethyl)benzoyl)glycinewas synthesized according to the reaction schemes shown in Chem. 21 andChem. 22 and following the procedure described below.

1,3-dibromo-5-(trifluoromethyl)benzene (1, 3.03 g, 10.00 mmol) wasdissolved in dry diethyl ether (25 mL) and cooled to −78° C.n-Butyllithium (4.24 mL, 2.35 M in hexanes, 10.0 mmol) was addeddrop-wise with stirring. After 15 minutes, dry N,N-dimethylformamide(1.44 mL, 20.0 mmol) was added in one portion and the resulting mixturewas allowed to warm to ambient temperature over an hour. 1 M aqueoussolution of hydrochloric acid (30 mL) was then added to quench thereaction and the reaction mixture was taken up in diethyl ether (30 mL)and washed with water (20 mL) and brine (20 mL), dried over anhydroussodium sulfate, filtered and evaporated. The crude product was purifiedby flash column chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/ethyl acetate 20:1) to give 3-bromo-5-(trifluoromethyl)benzaldehyde (2) as colorless oil.

Yield: 1366 mg (54%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 10.02 (s, 1H); 8.20 (bs, 1H);8.07 (bs, 1H); 8.02 (bs, 1H).

Methyl 3-bromo-5-iodobenzoate (3, 1.36 g, 4.00 mmol) was dissolved indry tetrahydrofuran (12 mL) and cooled to −30° C. Isopropylmagnesiumchloride-lithium chloride complex (3.11 mL, 1.3 M solution intetrahydrofuran, 4.20 mmol) was added drop-wise with stirring. After 30minutes, 3-bromo-5-(trifluoromethyl)benzaldehyde (2, 1.21 g, 4.80 mmol)was added with aid of 3 mL of tetrahydrofuran. The resulting mixture wasallowed to warm to ambient temperature and quenched after one hour bythe addition of 1 M aqueous solution of hydrochloric acid (15 mL). Thereaction mixture was taken up in diethyl ether (50 mL), washed withwater (30 mL) and brine (30 mL), dried over anhydrous sodium sulfate,filtered and evaporated. The crude product (4) was dissolved in drydichloromethane (20 mL) and pyridinium chlorochromate (1.29 g, 6.00mmol) was added with stirring. After stirring for 17 hours, the reactionmixture was filtered through a plug of silica (15 g) topped with Celiteand the bed was washed with dichloromethane (3×20 mL). The yellowishsolution was concentrated in vacuo and the residue was purified by flashcolumn chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/dichloromethane 6:1 to 1:1) to give methyl3-bromo-5-(3-bromo-5-(trifluoromethyl)benzoyl)benzoate (5) as colorlesssolid.

Yield: 1620 mg (87%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.45 (t, J=1.4 Hz, 1H); 8.29(m, 1H); 8.12 (t, J=1.6 Hz, 1H); 8.08 (bs, 1H); 8.04 (bs, 1H); 7.95 (bs,1H); 3.97 (s, 3H).

Methyl 3-bromo-5-(3-bromo-5-(trifluoromethyl)benzoyl)benzoate (1, 1071mg, 2.30 mmol) and Deoxo-Fluor (3.00 mL) were charged to a 25 mLreaction vessel. The vessel was sealed, purged with nitrogen and heatedto 90° C. (oil bath) for 16 hours. The reaction mixture was cooled toambient temperature and diluted with dichloromethane (50 mL). Theresulting solution was added slowly to a saturated aqueous potassiumhydrogencarbonate solution (100 mL) and the biphasic mixture was stirredfor an hour to decompose the excess of fluorinating reagent. The layerswere separated and the organic layer was dried over anhydrous sodiumsulfate, filtered and evaporated. The crude product was purified byflash column chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/ethyl acetate 30:1 to 15:1) to give methyl3-bromo-5-((3-bromo5-(trifluoromethyl)phenyl)difluoromethyl) benzoate(2) as yellowish oil.

Yield: 1096 mg (97%)

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.30 (s, 1H); 8.08 (s, 1H);7.88 (s, 1H); 7.83 (s, 1H); 7.81 (s, 1H); 7.71 (s, 1H); 3.96 (s, 3H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −62.87 (s, 3H); −90.00 (s,2H).

3-Bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)difluoromethyl) benzoate(2, 1096 mg, 2.25 mmol) dissolved in tetrahydrofuran (8 mL), methanol (4mL) and water (2 mL). Lithium hydroxide monohydrate (377 mg, 9.00 mmol)was added and the resulting mixture was stirred for 16 hours; and thenit was taken up in ethyl acetate (40 mL) and washed with 1 M aqueoussolution of hydrochloric acid (30 mL) and brine (30 mL); dried overanhydrous sodium sulfate; filtered and evaporated to give the crude3-bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)difluoromethyl)benzoicacid (3) as a white solid. It was dissolved in anhydrous acetonitrile(10 mL) and carbonyldiimidazole (CDI, 437 mg, 2.69 mmol) was added.After 30 minutes, glycine tert-butyl ester hydrochloride (564 mg, 3.37mmol) was added and the resulting mixture was stirred for an hour atambient temperature. The reaction mixture was evaporated in vacuo andthe residue was taken up in ethyl acetate (40 mL) and the organic layerwas washed 1 M aqueous solution of hydrochloric acid (30 mL) and brine(30 mL), dried over anhydrous sodium sulfate and evaporated. Theresulting gum was triturated with n-hexane (12 mL) to inducecrystallization and the resulting solid was collected by filtration,washed with n-hexane (2×6 mL) and dried in vacuo to give tert-butyl(3-bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)difluoromethyl)benzoyl)glycinate(4) as colorless solid.

Yield: 1220 mg (92%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.03 (s, 1H); 7.88 (s, 1H);7.86 (s, 1H); 7.79 (s, 1H); 7.75 (s, 1H); 6.86 (m, 1H); 6.86 (s, 1H);4.12 (d, J=4.9 Hz, 2H); 1.50 (s, 9H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −62.85 (s, 3H); −89.85 (s,2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 2.70 min.

LC-MS m/z: 532.2 (M+H)⁺

A 100 mL reaction vessel was charged with potassium acetate (735 mg,7.50 mmol) and the salt was dried for 1 hour at 110° C. in vacuo. Aftercooling to room temperature, the reaction vessel was backfilled withnitrogen and charged with tert-butyl(3-bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)difluoromethyl)benzoyl)glycinate(4, 880 mg, 1.50 mmol), palladium acetate (4.6 mg, 60.0 μmol),2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos, 57 mg, 120μmol) and bis(pinacolato)diboron (838 mg, 3.30 mmol). The reactionvessel was then evacuated and backfilled with nitrogen (this procedurewas repeated twice). Anhydrous tetrahydrofuran (8.0 mL) was added withsyringe, the vessel was sealed with a plastic stopper and submerged inthe heating bath preheated to 60° C. After stirring at 400 rpm for 4hours the reaction mixture was cooled to ambient temperature, dilutedwith dichloromethane (15 mL) and filtered through a short plug of silica(10 g) topped with Celite S with the aid of dichloromethane (3×20 mL).The filtrate was concentrated under reduced pressure to affordtert-butyl(3-(difluoro(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)methyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)glycinate(5) as orange foam.

It was dissolved in dry dichloromethane (4.0 mL) and trifluoroaceticacid (4.0 mL) was added and the resulting mixture was stirred for 1 hourat room temperature. Volatiles were evaporated under reduced pressureand the residue was co-distilled with toluene (3×10 mL. The residue wasdissolved in acetonitrile (9.0 mL) and water (3.0 mL), periodic acid(1368 mg, 6.00 mmol) was added and reaction mixture was stirred for 2hours. The mixture was diluted with ethyl acetate (40 mL) and washedwith water (2×30 mL) and brine (30 mL). Organic phase was dried overanhydrous sodium sulphate, filtered and concentrated under reducedpressure to give a yellowish foam. The foam was dissolved in wet ethylacetate (5 mL) and n-hexane (15 mL) was added. The mixture was left tostir overnight and the precipitated product was collected by filtration,washed with n-hexane (2×6 mL) and dissolved in acetonitrile (15 mL). Thesolution was freeze-dried to afford the title(3-borono-5-((3-borono-5-(trifluoromethyl)phenyl)difluoromethyl)benzoyl)glycine (6) as colorless solid.

Yield: 558 mg (81%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂O 10:1, δ_(H)): 8.48 (s, 1H);8.38 (m, 1H, exchanges with D₂O); 8.29 (s, 1H); 8.25 (s, 1H); 8.20 (app.s, 2H); 7.94 (s, 1H); 4.16-4.09 (m, 2H).

¹⁹F NMR spectrum (282 MHz, Acetone-d₆/D₂O 10:1, δ_(F)): −63.07 (s, 3H);−89.89 (s, 2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 2.92 min.

LC-MS m/z: 462.4 (M+H)⁺.

Example 19(3-Borono-5-(3-borono-5-(trifluoromethyl)benzoyl)benzoyl)glycine

(3-Borono-5-(3-borono-5-(trifluoromethyl)benzoyl)benzoyl)glycine wassynthesized according to the reaction scheme shown in Chem. 23 andfollowing the procedure described below.

1,3-dibromo-5-(trifluoromethyl)benzene (1, 3.03 g, 10.00 mmol) wasdissolved in dry diethyl ether (25 mL) and cooled to −78° C.n-Butyllithium (4.24 mL, 2.35 M in hexanes, 10.0 mmol) was addeddrop-wise with stirring. After 15 minutes, dry N,N-dimethylformamide(1.44 mL, 20.0 mmol) was added in one portion and the resulting mixturewas allowed to warm to ambient temperature over an hour. 1 M aqueoussolution of hydrochloric acid (30 mL) was then added to quench thereaction and the reaction mixture was taken up in diethyl ether (30 mL)and washed with water (20 mL) and brine (20 mL), dried over anhydroussodium sulfate, filtered and evaporated. The crude product was purifiedby flash column chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/ethyl acetate 20:1) to give 3-bromo-5-(trifluoromethyl)benzaldehyde (2) as colorless oil.

Yield: 1366 mg (54%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 10.02 (s, 1H); 8.20 (bs, 1H);8.07 (bs, 1H); 8.02 (bs, 1H).

Methyl 3-bromo-5-iodobenzoate (3, 1.36 g, 4.00 mmol) was dissolved indry tetrahydrofuran (12 mL) and cooled to −30° C. Isopropylmagnesiumchloride-lithium chloride complex (3.11 mL, 1.3 M solution intetrahydrofuran, 4.20 mmol) was added drop-wise with stirring. After 30minutes, 3-bromo-5-(trifluoromethyl)benzaldehyde (2, 1.21 g, 4.80 mmol)was added with aid of 3 mL of tetrahydrofuran. The resulting mixture wasallowed to warm to ambient temperature and quenched after one hour bythe addition of 1 M aqueous solution of hydrochloric acid (15 mL). Thereaction mixture was taken up in diethyl ether (50 mL), washed withwater (30 mL) and brine (30 mL), dried over anhydrous sodium sulfate,filtered and evaporated. The crude product (4) was dissolved in drydichloromethane (20 mL) and pyridinium chlorochromate (1.29 g, 6.00mmol) was added with stirring. After stirring for 17 hours, the reactionmixture was filtered through a plug of silica (15 g) topped with Celiteand the bed was washed with dichloromethane (3×20 mL). The yellowishsolution was concentrated in vacuo and the residue was purified by flashcolumn chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/dichloromethane 6:1 to 1:1) to give methyl3-bromo-5-(3-bromo-5-(trifluoromethyl)benzoyl)benzoate (5) as colorlesssolid.

Yield: 1620 mg (87%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.45 (t, J=1.4 Hz, 1H); 8.29(m, 1H); 8.12 (t, J=1.6 Hz, 1H); 8.08 (bs, 1H); 8.04 (bs, 1H); 7.95 (bs,1H); 3.97 (s, 3H).

Methyl 3-bromo-5-(3-bromo-5-(trifluoromethyl)benzoyl)benzoate (5, 466mg, 1.00 mmol) was dissolved in tetrahydrofuran (3 mL), methanol (2 mL)and water (1 mL). Lithium hydroxide monohydrate (210 mg, 5.00 mmol) wasadded and the resulting mixture was stirred for 16 hours; and then itwas taken up in ethyl acetate (30 mL) and washed with 1 M aqueoussolution of hydrochloric acid (15 mL) and brine (15 mL); dried overanhydrous sodium sulfate; filtered and evaporated. The resulting solid(6) was added to a solution of1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium3-oxide hexafluorophosphate (HATU, 399 mg, 1.05 mmol) in dryN,N-dimethylformamide (5 mL), followed by addition of triethylamine(0.70 mL, 5.00 mmol). After ten minutes, glycine tert-butyl esterhydrochloride (250 mg, 1.50 mmol) was added and the resulting mixturewas stirred for one hour at ambient temperature. The reaction mixturewas diluted 1 M aqueous solution of hydrochloric acid (15 mL) and theprecipitated gummy solid was collected by filtration and dried in air.The resulting solid was triturated with n-hexane (5 mL), collected byfiltration and dried in vacuo to give tert-butyl2-(3-bromo-5-(3-bromo-5-(trifluoromethyl)benzoyl)benzamido)acetate (7)as colorless solid.

Yield: 311 mg (55%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.23 (t, J=1.7 Hz, 1H); 8.09(t, J=1.5 Hz, 1H); 8.07 (bs, 1H); 8.06-8.01 (m, 2H); 7.96 (bs, 1H); 6.67(t, J=3.8 Hz, 1H); 4.15 (d, J=4.8 Hz, 2H); 1.52 (s, 9H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 2.18 min.

LC-MS m/z: 566.3 (M+H)+

A 20 mL reaction vessel was charged with potassium acetate (202 mg, 2.06mmol) and the salt was dried for 1 hour at 110° C. in vacuo. Aftercooling to room temperature, the reaction vessel was backfilled withnitrogen and charged with tert-butyl2-(3-bromo-5-(3-bromo-5-(trifluoromethyl)benzoyl)benzamido)acetate (7,290 mg, 513 μmol), palladium acetate (4.6 mg, 10 μmol),2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos, 19.5 mg,51 μmol) and bis(pinacolato)diboron (287 mg, 1.13 mmol). The reactionvessel was then evacuated and backfilled with nitrogen (this procedurewas repeated twice). Anhydrous tetrahydrofuran (4 mL) was added withsyringe, the vessel was sealed with a plastic stopper and submerged inthe heating bath preheated to 60° C. After stirring at 400 rpm for 4hours the reaction mixture was cooled to ambient temperature, dilutedwith dichloromethane (15 mL) and filtered through a short plug of silica(15 g) topped with Celite S with the aid of dichloromethane (3×10 mL).The filtrate was concentrated under reduced pressure to affordtert-butyl(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)benzoyl)benzoyl)glycinate(8) as yellow waxy foam.

Yield: 340 mg (quantitative).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 5.57 min, 3.97 min

LC-MS m/z: 604.5 (M+H-tBu)⁺, 522.5 (M-pinacol-tBu+H)⁺

tert-Butyl(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)benzoyl)benzoyl)glycinate(8, 340 mg, 513 μmol) was mixed with trifluoroacetic acid (2 mL) andstirred for 1 hour at room temperature. Volatiles were evaporated underreduced pressure. The residue and periodic acid (600 mg, 2.63 mmol) weredissolved in acetonitrile/water mixture (4:1, 2.5 mL), and reactionmixture was stirred for 2 hours. The mixture was diluted with ethylacetate (5 mL) and washed with water (5 mL) and brine (5 mL). Organicphase was concentrated under reduced pressure to give yellow solid,which was purified by preparative LC/MS (SunFire Prep C18, 5 μm, 19×100mm, acetonitrile/water 5:95 to 100:0+0.1% FA). Pure fractions werecollected and freeze-dried to afford the title product (9) as whitesolid.

Yield: 101 mg (49%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂O 10:1, δ_(H)): 8.66 (s, 1H);8.48 (s, 1H); 8.40 (m, 3H); 8.15 (s, 1H); 4.16 (m, 2H).

¹⁹F NMR spectrum (282 MHz, Acetone-d₆/D₂O 10:1, δ_(F)): 63.13 (s).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.34 min.

LC-MS m/z: 440.3 (M+H)⁺.

Example 20(3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)sulfonyl)glycine

(3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)sulfonyl)glycine wassynthesized according to the reaction scheme shown in Chem. 24 andfollowing the procedure described below.

1,3-Dibromo-5-(trifluoromethyl) benzene (1, 5.74 g, 18.0 mmol) was addedto a mixture of copper(II) sulfate pentahydrate (225 mg, 1.80 mmol) andpotassium hydroxide (5.03 g, 180 mmol) in mixture dimethylsulfoxide/water (10:1, 38 mL), reaction flask was filled with nitrogenand at the end was added 1,2-ethanedithiol (2.68 mL, 60.0 mmol) throughthe septum. Reaction mixture was heated to 110° C. overnight. Then wasmixture acidified to pH=2 with 1 M aqueous solution of hydrochloric acidand extracted with ethyl acetate. After drying over anhydrous sodiumsulfate and filtration solvent was evaporated under reduced pressure.Residue was purified by column chromatography (Silicagel 60, 0.063-0.200mm; eluent: cyclohexane) to give 3-bromo-5-(trifluoromethyl)benzenethiol(2) as yellow oil.

Yield: 2.27 g (51%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.61 (s, 1H); 7.56 (s, 1H);7.46 (s, 1H); 3.66 (s, 1H).

3-Bromo-5-iodobenzoic acid (40.0 g, 122 mmol) was dissolved in methanol,methanesulfonic acid (3 mL) was added and reaction mixture was heated to60° C. overnight, then was reaction cooled to 0° C. with stirring andthen was kept in freezer overnight. Methyl 3-bromo-5-iodobenzoate (3)was obtained by filtration as white solid.

Yield: 34.5 g (83%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.31 (t, J=1.34 Hz, 1H); 8.15(t, J=1.50 Hz, 1H); 8.05 (t, J=1.59 Hz, 1H); 3.95 (s, 3H).

3-Bromo-5-(trifluoromethyl)benzenethiol (2, 2.27 g, 8.80 mmol), methyl3-bromo-5-iodobenzoate (3, 1.85 g, 5.50 mmol), potassium carbonate (1.51g, 10.9 mmol) and copper(I) iodide (207 mg, 1.09 mmol) were dissolved indry dimethoxyethane (22 mL). Reaction flask was heated to 80° C. for 48hours. After this time was mixture diluted with ethyl acetate andfiltrated through the Celite S, solvent was then evaporated underreduced pressure. Residue was purified by column chromatography(Silicagel 60, 0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 1:0 to20:1) to give methyl3-bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)thio)benzoate (4) asyellow oil.

Yield: 1.93 g (75%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.82, 1H); 7.68 (m, 3H); 7.52(m, 1H); 2.54 (s, 3H).

Methyl 3-bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)thio)benzoate (4,1.93 g, 4.10 mmol) and potassium peroxymonosulfate (3.80 g, 6.30 mmol)were suspended in methanol (22 mL) and water (11 mL) was added. Thereaction was stirred overnight at room temperature. Then was mixturediluted with ethyl acetate (20 mL), washed with water (30 mL) and thenwith brine (30 mL). Organic phase was evaporated under reduced pressure,residue was chromatographed by column chromatography (Silicagel 60,0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 9:1 to 3:1) to givemethyl 3-bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)sulfonyl)benzoate(5) as white solid.

Yield: 1.30 g (63%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.53 (m, 1H); 8.43 (m, 1H);8.27 (m, 2H); 8.16 (m, 1H); 8.01 (m, 1H); 4.00 (s, 3H).

Methyl 3-bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)sulfonyl)benzoate(5, 1.30 g 2.60 mmol) and lithium hydroxide monohydrate (330 mg, 7.80mmol) were dissolved in mixture of methanol/water/tetrahydrofurane(4:2:5, 23 mL), reaction mixture was stirred overnight at roomtemperature. After this time was mixture acidified to pH=2 with 1 Maqueous solution of hydrochloric acid and extracted with ethyl acetate.After evaporation of all volatiles was obtained3-bromo-5-((3-bromo-5-(trifluoromethyl) phenyl)sulfonyl)benzoic acid (6)as white solid.

Yield: 1.18 g (93%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 13.91 (bs, 1H); 8.68 (s, 2H);8.50 (s, 1H); 8.45 (s, 1H); 8.41 (s, 1H); 8.32 (s, 1H).

3-Bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)sulfonyl)benzoic acid (6,1.18 g, 2.40 mmol) mixed with1-((dimethylamino)(dimethyliminio)methyl)-1H-[1,2,3]triazolo[4,5-b]pyridine3-oxide hexafluorophosphate(V) (HATU, 1.01 g, 2.64 mmol) in dryN,N′-dimethylformamide (30 mL) for 30 minutes, then triethylamine (1.22g, 12.0 mmol) was added and glycine tert-butyl ester hydrochloride (810mg, 4.80 mmol), after end of reaction was added water and reactionmixture was extracted with ethyl acetate (25 mL), after evaporation ofall volatiles under reduced pressure was residue purified by columnchromatography (Silicagel 60, 0.063-0.200 mm; eluent: cyclohexane/ethylacetate 3:1) to give tert-butyl(3-bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)sulfonyl)benzoyl)glycinate(7) as white solid.

Yield: 1.00 g (69%).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 4.30 min.

LC-MS m/z: 602.3 (M+H)⁺.

A 50 mL reaction flask was charged with potassium acetate (815 mg, 8.30mmol) and the salt was dried for 1 hour at 110° C. in vacuo. Aftercooling to room temperature, the reaction flask was backfilled withnitrogen and charged with tert-butyl(3-bromo-5-((3-bromo-5-(trifluoromethyl)phenyl)sulfonyl)benzoyl)glycinate(7, 1.00 g, 1.66 mmol), palladium acetate (19.0 mg, 82.0 μmol),2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos, 79 mg, 165μmol) and bis(pinacolato)diboron (930 mg, 3.60 mmol). The reaction flaskwas then evacuated and backfilled with nitrogen (this procedure wasrepeated twice), anhydrous tetrahydrofuran (8 mL) was added withsyringe, the flask was sealed with a plastic stopper and heated to 60°C. Reaction mixture was stirred overnight and then was cooled to ambienttemperature, diluted with dichloromethane (30 mL) and filtered through ashort plug of silicagel topped with Celite S and washed withdichloromethane (3×10 mL. The filtrate was concentrated under reducedpressure to afford the tert-butyl(3-(4,4,5,5-tetramethyl-1,3,2-dioxaboroloan-2-yl)-5-((3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)sulfonyl)benzoyl)glycinate (8) as brown waxy foam.

Yield: 1.16 g (quantitative).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 5.40 min, 3.97 min, 2.62 min

LC-MS m/z: 640.5 (M+H-tBu)⁺, 558.4 (M-pinacol-tBu+H)⁺, 476.3(M-2pinacol-tBu+H)⁺.

tert-Butyl(3-(4,4,5,5-tetramethyl-1,3,2-dioxaboroloan-2-yl)-5-((3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)sulfonyl)benzoyl)glycinate (8, 1.16 g, 1.66 mmol) was mixed with trifluoroacetic acid (5mL) and stirred 1 hour at room temperature, after this time allvolatiles was evaporated under reduced pressure.(3-(4,4,5,5-Tetramethyl-1,3,2-dioxaboroloan-2-yl)-5-((3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)sulfonyl)benzoyl)glycine(9) was obtained as brown waxy foam.

Yield: 1.06 g (quantitative).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 4.31 min, 2.89 min, 1.12

LC-MS m/z: 640.5 (M+H)+, 558.4 (M-pinacol+H)⁺, 476.3 (M-2pinacol+H)⁺.

(3-(4,4,5,5-Tetramethyl-1,3,2-dioxaboroloan-2-yl)-5-((3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)sulfonyl)benzoyl)glycine(9, 1.16 g, 1.16 mmol) and periodic acid (430 mg, 4.64 mmol) weredissolved in acetonitrile/water (mixture 4:1, 5 mL), reaction mixturewas stirred 2 hours. Then was mixture diluted with ethyl acetate (10 mL)and washed with water (10 mL) and brine (10 mL). Organic phase wasconcentrated under reduced pressure, as residue was obtained yellowsolid, from which was removed part, which was purified by preparativeLC/MS (SunFire Prep C18, 5 μm, 19×100 mm, acetonitrile/water 5:95 to100:0+0.1% FA). All solvents were freeze-dried and(3-borono-5-((3-borono-5-(trifluoromethyl)phenyl)sulfonyl)benzoyl)glycine(10) was obtained as white solid.

Yield: 110 mg (14%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂O 10:1, δ_(H)): 8.69 (s, 1H);8.59 (m, 3H); 8.36 (s, 1H); 8.33 (s, 1H); 4.13 (m, 2H). ¹⁹F NMR spectrum(282 MHz, Acetone-d₆/D₂O 10:1, δ_(F)): 63.16 (s).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.34 min.

LC-MS m/z: 476.3 (M+H)⁺.

Example 214-((3S,4S)-3,4-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoicacid

4-((3S,4S)-3,4-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoicacid was synthesized according to the reaction schemes shown in Chem. 25and Chem. 26 and following the procedure described below.

2,5-Dioxopyrrolidin-1-yl 4-((3S,4S)-3,4-bis((tert-butoxycarbonyl)amino)pyrrolidin-1-yl)-4-oxobutanoate (1, 1.50 g, 3.01 mmol) was dissolved intetrahydrofuran/water mixture (1:1, 10 mL) and left to stay for 7 days.The mixture was diluted with ethyl acetate (50 mL) and washed with water(2×50 mL) and brine (1×50 mL). Organic layer was dried over anhydroussodium sulfate, filtered and evaporated to dryness affording4-((3S,4S)-3,4-bis((tert-butoxycarbonyl)amino)pyrrolidin-1-yl)-4-oxobutanoic acid (2) as white solid.

Yield: 1.15 g (95%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 5.58-5.45 (m, 1H); 5.41-5.30(m, 1H); 4.12-3.80 (m, 4H); 3.35-3.17 (m, 2H); 2.76-2.39 (m, 4H); 1.45(s, 18H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 2.97 min.

LC-MS m/z: 401.4 (M+H)⁺.

The acid (2, 1.14 g, 2.83 mmol) was dissolved in dichloromethane (5 mL)and 4 M solution of hydrogen chloride in 1,4-dioxane (20 mL) was added.After 30 minutes the solvent was evaporated. The residue was suspendedin diethyl ether (10 mL), decanted and dried in vacuo to yield4-((3S,4S)-3,4-diaminopyrrolidin-1-yl)-4-oxobutanoic aciddihydrochloride (3) as pale brown powder.

Yield: 0.78 g (100%).

¹H NMR spectrum (300 MHz, D₂O, δ_(H)): 4.33-4.17, 3H); 4.10-3.99 (m,1H); 3.92-3.83 (m, 1H); 3.78-3.68 (m, 1H); 2.67 (s, 4H).

4-((3S,4S)-3,4-Diaminopyrrolidin-1-yl)-4-oxobutanoic aciddihydrochloride (1, 0.16 g, 0.59 mmol) was dissolved in water (3 mL).Then N,N-dimethylformamide (3 mL), N,N-diisopropylethylamine (0.51 mL,2.95 mmol) and 2,5-dioxopyrrolidin-1-yl7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (2,0.34 g, 1.17 mmol) were added. Resulting mixture was stirred overnightat room temperature. The mixture was acidified with 1 M aqueous solutionof hydrochloric acid and solvents were evaporated. The residue wasdissolved in ethyl acetate (40 mL) and washed with water (2×20 mL).Organic layer was dried over anhydrous sodium sulfate, filtered andevaporated. The residue was purified by preparative LC/MS (SunFire PrepC18, 5 μm, 19×100 mm, acetonitrile/water 5:95 to 100:0+0.1% FA) to givethe title compound (3) as white solid.

Yield: 16.0 mg (5%).

Total yield: 16.0 mg (5%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.39 (s, 2H); 8.73-8.63 (m,2H); 7.75-7.65 (m, 2H); 7.34-7.27 (m, 2H); 5.03 (s, 4H); 4.63-4.48 (m,2H); 3.99-3.88 (m, 1H); 3.82-3.72 (m, 1H); 3.47-3.22 (m, 2H); 2.47-2.39(m, 4H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.05 min.

LC-MS m/z: 557.0 (M+H)⁺.

Example 22 (3-Borono-5-(3-borono-5-fluorobenzoyl)benzoyl)glycine

(3-Borono-5-(3-borono-5-fluorobenzoyl)benzoyl)glycine was synthesizedaccording to the reaction scheme shown in Chem. 27 and following theprocedure described below.

3-(3-Fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoicacid (1, 546 mg, 1.10 mmol) and1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium3-oxide hexafluorophosphate (HATU, 439 mg, 1.16 mmol) were dissolved indry DMF (5 mL) and triethylamine (0.76 mL, 5.50 mmol) was added. Afterten minutes, glycine tert-butyl ester hydrochloride (277 mg, 1.65 mmol)was added and the resulting mixture was stirred for an hour at ambienttemperature. The reaction mixture was taken up in ethyl acetate (25 mL)and washed with 0.5 M aqueous solution of hydrochloric acid (2×15 mL),5% aqueous solution of lithium chloride (2×15 mL), 5% aqueous solutionof potassium hydrogencarbonate (1×15 mL) and brine (15 mL), dried overanhydrous sodium sulfate and evaporated to give a compound 2 asyellowish powder. Solid was dissolved in acetonitrile (6 mL) and water(1.5 mL) and periodic acid (912 mg, 4.00 mmol) was added. After onehour, the reaction mixture was taken up in ethyl acetate (25 mL) andwashed with water (2×15 mL) and brine (15 mL), dried over anhydroussodium sulfate and evaporated to give a yellowish foam, which wasdissolved in trifluoroacetic acid (5 mL) and stirred for one hour.Volatiles were removed in vacuo and the residue co-evaporated with ethylacetate (3×15 mL) to give a beige solid, which was triturated withdiethyl ether (5 mL) and cyclohexane (5 mL). The resulting solid wascollected by filtration, washed with cyclohexane (2×5 mL) and dried invacuo to give the title3-borono-5-(3-borono-5-fluorobenzoyl)benzoyl)glycine (3) as colorlesssolid.

Yield: 394 mg (92%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂O, δ_(H)): 8.60 (d, J=0.6 Hz,1H); 8.35 (dd, J=8.2, 1.5 Hz, 2H); 8.04 (s, 1H); 7.80 (ddd, J=9.2, 2.7,0.8 Hz, 1H); 7.62-7.49 (m, 1H); 4.12 (s, 2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 05:95 to100:0+0.1% FA): 3.11 min.

LC-MS m/z: 390.4 (M+H)⁺

Example 24(3-Borono-5-((3-borono-5-fluorophenyl)sulfonyl)benzoyl)glycine

(3-Borono-5-((3-borono-5-fluorophenyl)sulfonyl)benzoyl)glycine wassynthesized according to the reaction scheme shown in Chem. 29 andfollowing the procedure described below.

A mixture of 3-bromo-5-fluorobenzenethiol (1, 1.55 g, 7.49 mmol), methyl3-bromo-5-iodobenzoate (2, 2.81 g, 8.24 mmol), copper(I) iodide (143 mg,749 μmol), potassium carbonate (2.07 g, 15.0 mmol) and dry1,2-dimethoxyetane (30.0 mL) was heated at 80° C. under argon overweekend. The reaction mixture was cooled to room temperature; dilutedwith ethyl acetate (30 mL); filtered over Celite and evaporated todryness. The residue was re-dissolved in ethyl acetate (100 mL); washedwith 0.5 M aqueous hydrochloric acid (50 mL), 0.5 M aqueous sodiumhydroxide (2×50 mL) and 0.5 M aqueous hydrochloric acid (50 mL); driedover anhydrous sodium sulfate and evaporated to dryness. The residue wassubjected to flash column chromatography (Silicagel 60, 0.040-0.063 mm;eluent: cyclohexane/ethyl acetate 97:3) to afford methyl3-bromo-5-((3-bromo-5-fluorophenyl)thio)benzoate (3) contaminated withmethyl 3-bromo-5-iodobenzoate (2) as pale yellow oil.

Yield: 2.54 g (40%).

Content: 50% (¹H NMR).

R_(F) (SiO₂, n-hexane/ethyl acetate 9:1): 0.50.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.13 (m, 1H); 7.99 (t, J=1.6Hz, 1H); 7.70 (t, J=1.7 Hz, 1H); 7.24 (td, J=1.6 and 0.6 Hz, 1H); 7.16(ddd, J=8.0, 2.3 and 1.7 Hz, 1H); 6.93 (ddd, J=8.5, 2.4 and 1.6 Hz, 1H);3.94 (s, 3H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)) −108.98 (s).

LC-MS purity: 73% (UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 3.47 min.

LC-MS m/z: 421.3 (M+H)⁺.

Potassium peroxymonosulfate (2.75 g, 4.48 mmol) was added to a solutionof the above methyl 3-bromo-5-((3-bromo-5-fluorophenyl)thio)benzoate (3,50%, 2.53 g, 2.99 mmol) in N,N-dimethylformamide (30 mL) and water (5mL) and the reaction mixture was stirred at room temperature overnight.One more portion of Oxone® (2.75 g, 4.48 mmol) was added and thereaction mixture was stirred at room temperature overnight. Solventswere removed in vacuo; 15% aqueous solution of potassiumhydrogencarbonate (60 mL) and 15% aqueous solution of sodium sulfite (60mL) were subsequently added to the residue followed by ethyl acetate(300 mL). The phases were separated; the organic one was washed withwater (100 mL) and brine (50 mL); dried over anhydrous sodium sulfateand evaporated to dryness. The residue was purified by flash columnchromatography (Silicagel 60, 0.040-0.063 mm; eluent: cyclohexane/ethylacetate 95:5 to 9:1) to give methyl3-bromo-5-((3-bromo-5-fluorophenyl)sulfonyl)benzoate (4) as white solid.

Yield: 1.23 g (91%).

R_(F) (SiO₂, n-hexane/ethyl acetate 9:1): 0.20.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.49 (i, 1H); 8.40 (dd, J=2.0and 1.5 Hz, 1H); 8.24 (t, J=1.8 Hz, 1H); 7.90 (td, J=1.6 and 0.6 Hz,1H); 7.62 (ddd, J=7.3, 2.3 and 1.6 Hz, 1H); 7.50 (ddd, J=7.7, 2.4 and1.7 Hz, 1H); 3.98 (s, 3H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −105.73 (s).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 4.14 min.

LC-MS m/z: 453.2 (M+H)⁺.

A solution of sodium hydroxide (535 mg, 13.4 mmol) in water (10 mL) wasadded to a solution of methyl3-bromo-5-((3-bromo-5-fluorophenyl)sulfonyl)benzoate (4, 1.21 g, 2.68mmol) in tetrahydrofuran (20 mL) and methanol (10 mL) and the resultingsolution was stirred at room temperature over weekend. The mixture wasconcentrated in vacuo; acidified with 1 M aqueous hydrochloric acid (25mL) and extracted with ethyl acetate (50 mL, 2×25 mL). Combined organicextracts were dried over anhydrous sodium sulfate and evaporated todryness. The residue was dissolved in anhydrous N,N-dimethylformamide(20 mL), followed by addition of 1-((dimethylamino)(dimethyliminio)methyl)-1H-[1,2,3]triazolo[4,5-b]pyridine 3-oxidehexafluorophosphate (V) (HATU, 1.12 g, 2.95 mmol) andN,N-diisopropylethylamine (1.84 mL, 10.7 mmol). The mixture was stirredat room temperature for 5 minutes; then tert-butyl glycinatehydrochloride (483 mg, 3.22 mmol) was added and stirring continued for 2hours. The reaction mixture was partitioned between 0.5 M aqueoushydrochloric acid (100 mL) and ethyl acetate (400 mL). The phases wereseparated and the organic one was washed with 0.5 M aqueous hydrochloricacid (100 mL), water (100 mL), 5% aqueous solution of sodium carbonate(100 mL) and brine; dried over anhydrous sodium sulfate and evaporatedto dryness. The residue was purified by flash column chromatography(Silicagel 60, 0.040-0.063 mm; eluent: cyclohexane/ethyl acetate 9:1) toafford tert-butyl(3-bromo-5-((3-bromo-5-fluorophenyl)sulfonyl)benzoyl)glycinate (5) ascolorless foam.

Yield: 900 mg (61%).

R_(F) (SiO₂, n-hexane/ethyl acetate 3:2): 0.55.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.26 (t, J=1.6 Hz, 1H);8.20-8.16 (m, 2H); 7.89 (td, J=1.5 and 0.7 Hz, 1H); 7.63-7.58 (m, 1H);7.52-7.47 (m, 1H); 6.75 (bs, 1H); 4.14 (d, J=5.0 Hz, 2H); 1.52 (s, 9H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −105.69 (s).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 50:50 to100:0+0.1% FA): 3.27 min.

LC-MS m/z: 552.2 (M+H)⁺.

A 50 mL reaction flask was charged with potassium acetate (533 mg, 5.43mmol) and the salt was dried for 1 hour at 110° C. in vacuo. Aftercooling to room temperature, the reaction flask was backfilled withargon and charged with tert-butyl(3-bromo-5-((3-bromo-5-fluorophenyl)sulfonyl)benzoyl)glycinate (5, 599mg, 1.09 mmol), palladium acetate (12.2 mg, 54.0 μmol),2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos, 51.8 mg,109 μmol) and bis(pinacolato)diboron (607 mg, 2.39 mmol). The reactionflask was then evacuated and backfilled with argon (this procedure wasrepeated twice), anhydrous tetrahydrofuran (7 mL) was added withsyringe, the flask was immersed in an oil bath pre-heated to 60° C.Reaction mixture was stirred at 60° C. for 20 hours, and then was cooledto ambient temperature, diluted with dichloromethane (7 mL) and filteredthrough a short plug of silicagel topped with Celite S and washed withdichloromethane (50 mL). The filtrate was concentrated under reducedpressure to afford the crude tert-butyl(3-((3-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)sulfonyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)glycinate(6) as yellow foam.

Yield: 772 mg (crude product).

R_(F) (SiO₂, n-hexane/ethyl acetate 3:2): 0.15.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.53-8.47 (m, 2H); 8.35 (dd,J=1.7 and 1.0 Hz, 1H); 8.17 (dd, J=1.7 and 0.8 Hz, 1H); 7.76-7.71 (m,1H); 7.70-7.64 (m, 1H); 6.75 (t, J=4.9 Hz, 1H); 4.15 (d, J=5.0 Hz, 2H);1.51 (s, 9H); 1.36 (s, 12H); 1.34 (s, 12H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)) −110.47 (s).

LC-MS purity: 96% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 50:50 to100:0+0.1% FA): 4.69 min.

LC-MS m/z: 646.7 (M+H)⁺.

A mixture of the above crude tert-butyl(3-((3-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)sulfonyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)glycinate(6, 772 mg, <1.09 mmol) and trifluoroacetic acid (8.00 mL) was stirredfor 1 hr at room temperature. The mixture was evaporated to dryness invacuo, and the residue was evaporated from dichloromethane (5×10 mL) toafford crude(3-((3-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)sulfonyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)glycine(7) as yellow foam.

Yield: 791 mg (crude product).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.54-8.48 (m, 2H); 8.43 (m,1H); 8.16 (dd, J=1.7 and 0.8 Hz, 1H); 7.76-7.71 (m, 1H); 7.70-7.65 (m,1H); 7.39 (t, J=5.3 Hz, 1H); 4.34 (d, J=5.3 Hz, 2H); 1.36 (s, 12H); 1.34(s, 12H).

LC-MS purity: 85% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 50:50 to100:0+0.1% FA): 3.16 min.

LC-MS m/z: 590.5 (M+H)⁺.

A solution of the above crude(3-((3-fluoro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)sulfonyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)glycine(7, 791 mg, <1.09 mmol) in acetonitrile (6.5 mL) was diluted with water(1.3 mL) followed by addition of periodic acid (991 mg, 4.35 mmol). Theresulting mixture was stirred for 1 hr; and then it was partitionedbetween ethyl acetate (80 mL) and water (20 mL). The phases wereseparated; the organic one was washed with brine (2×20 mL); dried overanhydrous sodium sulphate and evaporated to dryness. The residue wasdissolved in a minimal amount of wet ethyl acetate (3 mL) and theresulting solution was slowly added to stirred n-hexane (50 mL) cooledto 0° C. Precipitated solid was decanted and dried to give 472 mg ofcrude product (8). A portion of the solid (8, 172 mg) was purified bypreparative LC/MS (Synergi Polar-RP 80, 4 μm, 150×21.2 mm,acetonitrile/water 0:100 to 100:0+0.1% FA). Pure fractions were combinedand freeze-dried to give the title compound (8) as white powder.

Yield: 100 mg (59%).

R_(F) (SiO₂, acetonitrile/water/formic acid 89:10:1): 0.25.

¹H NMR spectrum (300 MHz, DMSO-d₆+DCl, δ_(H)): 8.55 (dd, J=1.7 and 1.2Hz, 1H); 8.50 (dd, J=1.8 and 1.1 Hz, 1H); 8.47 (t, J=1.8 Hz, 1H); 8.23(dd, J=1.7 and 0.7 Hz, 1H); 7.90-7.85 (m, 1H); 7.85-7.79 (m, 1H); 3.93(s, 2H).

¹⁹F NMR spectrum (282 MHz, DMSO-d₆+DCl, δ_(F)): −110.92 (s).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.12 min.

LC-MS m/z: 426.4 (M+H)⁺.

Example 25N-(1-Hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine

N-(1-Hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycinewas synthesized according to the reaction scheme shown in Chem. 30 andfollowing the procedure described below.

1-Bromopyrrolidine-2,5-dione (NBS, 34.9 g, 196 mmol) was added to asolution of 3-trifluoromethyl-4-methylbenzoic acid (1, 40.0 g, 196 mmol)in concentrated sulfuric acid (400 mL) and the reaction mixture wasallowed to stir at ambient temperature for 16 hours. The reactionmixture was then poured into ice-water (2 L). Resulting precipitate wasfiltered off, washed with water (500 mL) and dissolved in ethyl acetate(400 mL); dried over anhydrous sodium sulfate, filtered and evaporatedto provide 3-bromo-4-methyl-5-trifluoromethylbenzoic acid (2) as whitesolid.

Yield: 55.4 g (100%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 13.71 (bs, 1H); 8.35 (d,J=0.4 Hz, 1H); 8.15 (d, J=0.9 Hz, 1H); 2.56 (s, 3H).

Concentrated sulfuric acid (24 mL) was added to a solution3-bromo-4-methyl-5-trifluoromethylbenzoic acid (2, 35.0 g, 124 mmol) inmethanol (500 mL) and the reaction mixture was allowed to stir underreflux for 4 hours and at ambient temperature for 16 hours. The reactionmixture was then evaporated under reduced pressure, dissolved in diethylether (250 mL), extracted with water (2×100 mL) and mixture of saturatedsolution of potassium carbonate (100 mL) and brine (100 mL). Organiclayer was separated, dried over anhydrous sodium sulfate, filtered andevaporated to provide methyl 3-bromo-4-methyl-5-trifluoromethylbenzoate(3) as white solid.

Yield: 36 g (98%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 8.36 (d, J=1.1 Hz, 1H); 8.13(d, J=1.1 Hz, 1H); 3.90 (s, 3H); 2.55 (d, J=1.3 Hz, 3H).

The suspension of 1-bromopyrrolidine-2,5-dione (NBS, 32.3 g, 181 mmol)and methyl 3-bromo-4-methyl-5-trifluoromethylbenzoate (3, 35.9 g, 121mmol) in water (300 mL) was stirred for 6 hours under 100 W light bulbat 80° C. Reaction mixture was extracted with diethyl ether (2×200 mL).Organic layers were washed with brine (150 mL). Organic layer wasseparated, dried over anhydrous sodium sulfate, filtered and evaporatedto provide methyl 3-bromo-4-bromomethyl-5-trifluoromethylbenzoate (4) asyellow solid.

Yield: 45.5 g (100%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.47 d, J=1.5 Hz, 1H); 8.31 (d,J=1.3 Hz, 1H); 4.75 (s, 2H); 3.98 (s, 3H).

Solution of 3-bromo-4-bromomethyl-5-trifluoromethylbenzoate (4, 45.5 g,121 mmol) and potassium acetate (23.7 g, 142 mmol) in acetonitrile (0.5L) was stirred at 75° C. overnight. The suspension was filtered throughcotton-wool and evaporated. The crude product was dissolved indichloromethane and filtered again. Evaporation provided methyl3-bromo-4-(acetoxymethyl)-5-(trifluoromethyl)benzoate (5) as whitesolid.

Yield: 41.6 g (97%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)) 8.49 (d, J=1.3 Hz, 1H); 8.34 (d,J=1.3 Hz, 1H); 5.37 (s, 2H); 3.99 (s, 3H); 2.11 (s, 3H).

Solution of methyl 3-bromo-4-acetylmethyl-5-trifluoromethylbenzoate (5,40.5 g, 114 mmol), bis(pinacolato)diboron (31.9 g, 126 mmol), potassiumacetate (33.6 g, 343 mmol) and[1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (2.50 g,3.42 mmol) in dry tetrahydrofuran (500 mL) was allowed to stir at 75° C.under argon atmosphere for 12 days. Then the reaction mixture was cooledto ambient temperature, filtered and evaporated. The crude product wasfiltered through silica gel (Silicagel, 0.063-0.200 mm; eluent:cyclohexane/ethyl acetate 8:1) to provide methyl4-(acetoxymethyl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)benzoate(6).

Yield: 35.3 g (77%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 8:1): 0.40.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.65 (s, 1H); 8.43 (s, 1H);5.48 (s, 2H); 3.97 (s, 3H); 2.05 (s, 3H); 1.36 (s, 12H).

Solution of methyl4-(acetoxymethyl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)benzoate(6, 34.0 g, 84.6 mmol) and sodium hydroxide (17.0 g, 425 mmol) in water(300 mL) was stirred at ambient temperature for 3 hours. Then solutionof hydrochloric acid (35%, 37 mL) in water (100 mL) was added to lowerthe pH to 1. The reaction mixture was stirred overnight. Precipitate wasfiltered and dried to provide1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (7) as white solid.

Yield: 17.0 g (82%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 13.47 (bs, 1H); 9.66 (s, 1H);8.62 (s, 1H); 8.24 (s, 1H); 5.22 (s, 2H).

Solution of 2,3,4,5,6-pentafluorophenol (497 mg, 2.70 mmol),1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (7, 665 mg, 2.70 mmol) and N,N′-dicyclohexylcarbodiimide (DCC, 556mg, 2.70 mmol) in acetonitrile (15 mL) was stirred at ambienttemperature overnight. The reaction mixture was filtered, washed withacetonitrile and evaporated to give the perfluorophenyl1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(8) as white solid.

Yield: 1.00 g (91%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.79 (s, 1H); 8.86 (s, 1H);8.46 (s, 1H); 5.30 (s, 2H).

Solution of the perfluorophenyl1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(8, 850 mg, 2.06 mmol), (2-aminoethyl)glycine (9, 122 mg, 1.03 mmol) andtriethylamine (1.15 mL, 8.27 mmol) in N,N-dimethylformamide (25 mL) wasstirred at ambient temperature for 5 days. The reaction mixture was thenevaporated and crude product 10 was filtered through short pad of silicagel (eluent: dichloromethane/methanol 10:1 to 4:1), purified bypreparative HPLC (SunFire Prep C18, 5 μm, 19×100 mm, acetonitrile/water5:95 to 100:0+0.1% FA) and freeze-dried toN-(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine (10) as white solid.

Yield: 70.0 mg (12%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.91 (bs, 1H); 9.91-9.40 (m,2H); 9.02-8.65 (m, 1H); 8.67-7.41 (m, 4H); 5.28-5.03 (m, 4H); 4.37-3.90(m, 2H); 3.79-3.42 (m, 4H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.63 min.

LC-MS m/z: 575.5 (M+H)⁺.

Example 26(S)-2,3-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid

(S)-2,3-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid was synthesized according to the reaction scheme shown in Chem. 31and following the procedure described below.

1-Hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (1, 3.50 g, 14.2 mmol), N-hydroxysuccinimide (1.64 g, 14.2 mmol)and 1-ethyl-3-(3′-dimethylaminopropyl) carbodiimide hydrochloride (2.72g, 14.2 mmol) were stirred in tetrahydrofuran (70 mL) andN,N-dimethylformamide (10 mL) for 4 hours at ambient temperature. Thereaction mixture was evaporated and extracted with ethyl acetate (3×100mL) and 1 M aqueous solution of hydrochloric acid (100 mL). The organicphase was dried over anhydrous sodium sulfate, filtered and evaporatedto afford 2,5-dioxopyrrolidin-1-yl1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(2) as white solid.

Yield: 4.87 g (100%).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 2.32 min.

LC-MS m/z: 344.3 (M+H)⁺.

Solution of afforded 2,5-dioxopyrrolidin-1-yl1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(2, 515 mg, 1.50 mmol), (S)-2,3-diaminopropanoic acid hydrochloride (3,98.0 mg, 0.70 mmol) and N,N-diisopropylethylamine (0.75 mL, 4.20 mmol)in N,N-dimethylformamide (15 mL) and water (4 mL) was stirred at ambienttemperature overnight. The reaction mixture was evaporated, purified bypreparative HPLC (SunFire Prep C18, 5 μm, 19×100 mm, acetonitrile/water5:95 to 100:0+0.1% FA) and freeze-dried to afford(S)-2,3-bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid (4) as white solid.

Yield: 153 mg (39%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.90 (bs, 1H); 9.62 (d,J=4.2 Hz, 2H); 9.10 (d, J=8.1 Hz, 1H); 8.99 (t, J=5.2 Hz, 1H); 8.50 (d,J=15.0 Hz, 2H); 8.25 (d, J=21.1 Hz, 2H); 5.21 (d, J=5.5 Hz, 4H);4.84-4.63 (m, 1H); 3.99-3.81 (m, 1H); 3.79-3.59 (m, 1H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.70 min.

LC-MS m/z: 561.5 (M+H)⁺.

Example 274-((3S,4S)-3,4-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoicacid

4-((3S,4S)-3,4-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoicacid was synthesized according to the reaction scheme shown in Chem. 32and following the procedure described below.

2,5-Dioxopyrrolidin-1-yl 4-((3S,4S)-3,4-bis((tert-butoxycarbonyl)amino)pyrrolidin-1-yl)-4-oxobutanoate (1, 6.57 g, 13.2 mmol) was dissolved intetrahydrofuran/water mixture (1:1, 100 mL) and left to stay for 5 days.The mixture was diluted with ethyl acetate (100 mL) and washed with 1 Maqueous solution of hydrochloric acid (1×100 mL), water (2×100 mL) andbrine (1×100 mL). Organic layer was dried over anhydrous sodium sulfate,filtered and evaporated to dryness affording4-((3S,4S)-3,4-bis((tert-butoxycarbonyl)amino)pyrrolidin-1-yl)-4-oxobutanoicacid (2) as white solid.

Yield: 4.60 g (95%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 5.54-5.43 (m, 1H); 5.37-5.24(m, 1H); 4.11-3.80 (m, 4H); 3.33-3.17 (m, 2H); 2.74-2.42 (m, 4H); 1.45(s, 18H).

The acid (2, 4.59 g, 11.4 mmol) was dissolved in dichloromethane (10 mL)and 4 M solution of hydrogen chloride in 1,4-dioxane (100 mL) was added.After 30 minutes the solvent was evaporated. The residue was suspendedin ethyl acetate (100 mL), the insoluble material was filtered, washedwith ethyl acetate and dried in vacuo to yield4-((3S,4S)-3,4-diaminopyrrolidin-1-yl)-4-oxobutanoic aciddihydrochloride (3) as white powder.

Yield: 3.33 g (100%).

¹H NMR spectrum (300 MHz, D₂O, δ_(H)): 4.32-4.17 (m, 3H); 4.09-3.99 (m,1H); 3.91-3.84 (m, 1H); 3.77-3.68 (m, 1H); 2.67 (s, 4H).

Solution of 4-((3S,4S)-3,4-diaminopyrrolidin-1-yl)-4-oxobutanoic aciddihydrochloride (3, 137 mg, 0.50 mmol), 2,5-dioxopyrrolidin-1-yl1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(4, 343 mg, 1.00 mmol) and N,N-diisopropylethylamine (0.54 mL, 3.00mmol) in N,N-dimethylformamide (12 mL) and water (3 mL) was stirred atambient temperature overnight. The reaction mixture was evaporated,purified by preparative HPLC (SunFire Prep C18, 5 μm, 19×100 mm,acetonitrile/water 5:95 to 100:0+0.1% FA) and freeze-dried to afford4-((3S,4S)-3,4-bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoicacid (5) as white solid.

Yield: 103 mg (31%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)) 12.12 (bs, 1H); 9.63 (s, 2H);9.01 (dd, J=10.2 and 7.2 Hz, 2H); 8.48 (s, 2H); 8.23 (s, 2H); 5.20 (s,4H); 4.82-4.55 (m, 2H); 4.01 (dd, J=10.4 and 6.3 Hz, 1H); 3.86 (dd,J=12.3 and 7.0 Hz, 1H); 3.50 (dd, J=10.7 and 7.4 Hz, 2H); 2.49-2.37 (m,4H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.66 min.

LC-MS m/z: 658.7 (M+H)⁺.

Example 28(3-Borono-5-((3-borono-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl)benzoyl)glycine

(3-Borono-5-((3-borono-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl)-benzoyl)glycinewas synthesized according to the reaction scheme shown in Chem. 33 andfollowing the procedure described below.

N-Bromosuccinimide (25.2 g, 142 mmol) was added in ten equal portions toa mixture of pentafluoro(3-nitrophenyl)-λ⁶-sulfane (1, 23.3 g, 93.5mmol), trifluoroacetic acid (75 mL) and 98% sulfuric acid (25 mL) at 40°C. during 8 hours. The reaction mixture was stirred at 40° C. overnight.Then the mixture was portioned between ethyl acetate (0.5 L) andice-cold water (1 L). Organic phase was washed with 10% aqueous solutionof potassium carbonate (1 L), 10% aqueous solution of sodium sulfite (1L) and brine (1 L) prior to drying over anhydrous magnesium sulfate.Solvent was removed in vacuo and the residue was purified twice by flashcolumn chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/ethyl acetate 100:0 to 90:10) to give(3-bromo-5-nitrophenyl)pentafluoro-λ⁶-sulfane (2) as yellowishcrystalline solid.

Yield: 10.9 g (36%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.62-8.51 (m, 2H); 8.24 (t,J=1.7 Hz, 1H).

A thoroughly degassed mixture of(3-bromo-5-nitrophenyl)pentafluoro-λ⁶-sulfane (2, 5.88 g, 17.9 mmol),iron (5.01 g, 89.6 mmol) and ammonium chloride (9.59 g, 179 mmol) inmethanol/water (2:1, 36 mL) was heated under argon atmosphere to 90° C.for 1.5 hours. Insolubles were removed by filtration, and volatiles wereremoved under reduced pressure. The residue was dissolved in ethylacetate (400 mL) and washed with brine (2×500 mL) prior to drying overanhydrous magnesium sulfate. Solvent was removed in vacuo, and theresidue was purified by flash column chromatography (Silicagel 60,0.040-0.063 mm; eluent: cyclohexane/ethyl acetate 10:0 to 9:1) to give3-bromo-5-(pentafluoro-λ⁶-sulfanyl)aniline (3) as yellowish crystallinesolid.

Yield: 4.86 g (91%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.25 (t, J=1.7 Hz, 1H);7.02-6.89 (m, 2H); 3.95 (bs, 2H).

A solution of sodium nitrite (915 mg, 13.2 mmol) in water (10 mL) wasadded drop-wise to a mixture of3-bromo-5-(pentafluoro-λ⁶-sulfanyl)aniline (3, 3.76 g, 12.6 mmol) and35% hydrochloric acid (3.5 mL) in water (10 mL) at 0° C. The mixture wasstirred for further 30 minutes at 0° C. Then this solution was added toa solution of potassium O-ethyldithiocarbonate (5.05 g, 31.5 mmol) inwater (50 mL) at 50° C., and it was heated and stirred for further 60minutes. The mixture was cooled to room temperature and extracted withethyl acetate (300 mL). The organic phase was washed with 10% aqueoussolution of sodium hydroxide (500 mL), brine (500 mL), 0.5 M aqueoussolution hydrochloric acid (500 mL) and brine (500 mL) prior to dryingover anhydrous magnesium sulfate. Solvent was removed under reducedpressure. The residue was dissolved in ethanol (50 mL) and solution ofpotassium hydroxide (7.08 g, 126 mmol) in water (50 mL) was added. Theresulting mixture was heated to 80° C. for 12 hours. Volatiles wereremoved under reduced pressure. The residue was diluted with water (350mL) and washed with diethyl ether (500 mL). Aqueous phase was acidifiedwith 35% hydrochloric acid to pH 1 and then extracted with ethyl acetate(500 mL). Organic phase was washed with brine (2×500 mL) prior to dryingover anhydrous magnesium sulfate. Solvent was removed in vacuo and theresidue was purified by flash column chromatography (Silicagel 60,0.040-0.063 mm; eluent: cyclohexane) to give3-bromo-5-(pentafluoro-λ⁶-sulfanyl)benzenethiol (4) contaminated withunidentified inseparable impurities as colorless crystalline solid.

Yield: 1.64 g (<41%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.70-7.65 (m, 1H); 7.62-7.35(m, 2H); 3.69 (s, 1H).

A mixture of 3-bromo-5-(pentafluoro-λ⁶-sulfanyl)benzenethiol (4, 1.62 g,5.14 mmol), methyl 3-bromo-5-iodobenzoate (5, 1.75 g, 5.14 mmol),copper(I) iodide (98.0 mg, 0.51 mol), potassium carbonate (1.42 g, 10.3mmol) and dry 1,2-dimethoxyethane (20 mL) was heated at 80° C. underargon for 48 hours. The reaction mixture was cooled to room temperature;diluted with ethyl acetate (30 mL); filtered over Celite and evaporatedto dryness. The residue was dissolved in ethyl acetate (250 mL); washedwith 1 M aqueous solution of hydrochloric acid (250 mL) and brine (250mL); dried over anhydrous sodium sulfate and evaporated to dryness. Theresidue was subjected to flash column chromatography (Silicagel 60,0.040-0.063 mm; eluent: cyclohexane/ethyl acetate 100:0 to 98:2) to givemethyl3-bromo-5-((3-bromo-5-(pentafluoro-λ⁶-sulfanyl)phenyl)thio)benzoate (6)contaminated with methyl 3-bromo-5-iodobenzoate (5) as pale yellow oil.

Yield: 1.46 g.

Content: 60% (H NMR).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.16 (t, J=1.7 Hz, 1H); 8.01(t, J=1.7 Hz, 1H); 7.79 (t, J=1.7 Hz, 1H); 7.72 (t, J=1.7 Hz, 1H); 7.63(t, J=1.7 Hz, 1H); 7.51 (s, 1H); 3.94 (s, 3H).

Potassium peroxymonosulfate (2.52 g, 4.10 mmol) was added to a solutionof methyl3-bromo-5-((3-bromo-5-(pentafluoro-λ⁶-sulfanyl)phenyl)thio)benzoate (6,1.45 g, <2.74 mmol) in N,N-dimethylformamide (30 mL) and water (5 mL),and the reaction mixture was stirred at room temperature overnight. Onemore portion of potassium peroxymonosulfate (2.52 g, 4.10 mmol) wasadded and the reaction mixture was stirred at room temperatureovernight. Solvents were removed in vacuo; 15% aqueous solution ofpotassium hydrogencarbonate (60 mL) and 15% aqueous solution of sodiumsulfite (60 mL) were subsequently added to the residue followed by ethylacetate (300 mL). The phases were separated; the organic one was washedwith water (100 mL) and brine (50 mL); dried over anhydrous sodiumsulfate and evaporated to dryness. The residue was purified by flashcolumn chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/ethyl acetate 100:0 to 95:5) to give methyl3-bromo-5-((3-bromo-5-(pentafluoro-λ⁶-sulfanyl)phenyl) sulfonyl)benzoate(7) as white solid.

Yield: 421 mg (6% from 3).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.54-8.48 (m, 1H); 8.45-8.40(m, 1H); 8.28 (t, J=1.7 Hz, 1H); 8.26 (t, J=1.7 Hz, 1H); 8.21 (t, J=1.8Hz, 1H); 8.12 (t, J=1.8 Hz, 1H); 3.99 (s, 3H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 2.25 min.

LC-MS m/z: mass not found.

Solution of sodium hydroxide (169 mg, 4.22 mmol) in water (10 mL) wasadded to a solution of methyl3-bromo-5-((3-bromo-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl) benzoate(7, 472 mg, 10.9 mmol) in tetrahydrofuran/methanol (2:1, 30 mL). Themixture was stirred at room temperature for 20 hours. Volatiles wereremoved under reduced pressure. The residue was acidified with 1 Maqueous solution of hydrochloric acid (100 mL) and extracted with ethylacetate (2×150 mL). Combined organic phase was washed brine (250 mL)prior to drying over anhydrous magnesium sulfate. Solvent was removed invacuo to give 3-bromo-5-((3-bromo-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl)benzoic acid (8) as yellowish solid which was used in the nextstep without further purification.

Yield: 448 mg (97%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.57 (t, J=1.6 Hz, 1H);8.50-8.46 (m, 1H); 8.33-8.28 (m, 2H); 8.23 (t, J=1.8 Hz, 1H); 8.13 (t,J=1.8 Hz, 1H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 4.82 min.

LC-MS m/z: mass not found.

A mixture of3-bromo-5-((3-bromo-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl) benzoicacid (8, 448 mg, 0.82 mmol), tert-butyl glycinate hydrochloride (166 mg,0.99 mmol), N,N-diisopropylethylamine (0.57 mL, 3.29 mmol) and1-((dimethylamino)(dimethyliminio)methyl)-1H-[1,2,3]triazolo[4,5-b]pyridine 3-oxidehexafluorophosphate (V) (HATU, 344 mg, 0.91 mmol) in anhydrousN,N-dimethylformamide (20 mL) was stirred at room temperature for 16hours. The mixture was portioned between ethyl acetate (150 mL) and 0.5M aqueous solution of hydrochloric acid (150 mL). Organic phase waswashed brine (150 mL) prior to drying over anhydrous magnesium sulfate.Solvent was removed in vacuo and the residue was purified by flashcolumn chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/ethyl acetate 95:5 to 9:1) to give tert-butyl(3-bromo-5-((3-bromo-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl)benzoyl)glycinate (9) as colorless foam.

Yield: 462 mg (85%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.28 (s, 2H); 8.24-8.16 (m,3H); 8.12 (t, J=1.7 Hz, 1H); 6.70 (t, J=4.6 Hz, 1H); 4.14 (d, J=5.0 Hz,2H); 1.52 (s, 9H).

LC-MS purity: 100% (ELSD), 100% (UV, 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 50:50 to100:0+0.1% FA): 3.27 min.

LC-MS m/z: 604.2 (M-tBu)⁺.

A mixture of tert-butyl (3-bromo-5-((3-bromo-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl)benzoyl)glycinate (9, 444 mg, 0.67 mmol), palladiumacetate (8.00 mg, 34.0 μmol),2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos, 32.0 mg,67.0 μmol), bis(pinacolato)diboron (376 mg, 1.48 mmol) and potassiumacetate (330 mg, 3.36 mmol) in anhydrous tetrahydrofuran (25 mL) washeated under argon atmosphere at 60° C. for 23 hours. The mixture wascooled down to room temperature, diluted with dichloromethane (200 mL)and passed through a short plug of silica (Silicagel 60, 0.040-0.060 mm;eluent: dichloromethane). Solvents were removed under reduced pressureto give crude tert-butyl(3-((3-(pentafluoro-λ⁶-sulfanyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)sulfonyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoyl)glycinate (10) as brownish foam. It was dissolved indichloromethane (15 mL) and trifluoroacetic acid (15 mL) was added.Resulting solution was stirred at room temperature for 2 hours.Volatiles were removed under reduced pressure. The residue was dissolvedin aqueous acetonitrile (3:1, 50 mL) and periodic acid (617 mg, 2.70mmol) was added. Resulting mixture was stirred at room temperature forone hour.

Volatiles were removed under reduced pressure and the residue wasportioned between ethyl acetate (250 mL) and water (250 mL). Organicphase was washed with brine (250 mL) prior to drying over anhydrousmagnesium sulfate. Solvent was removed in vacuo and the residue waspurified twice by preparative LC/MS (SunFire Prep C18, 5 μm, 19×100 mm,acetonitrile/water 5:95 to 100:0+0.1% FA). Fractions containing productwere freeze-dried to give(3-borono-5-((3-borono-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl)benzoyl)glycine (11) as white solid.

Yield: 142 mg (40%).

¹H NMR spectrum (300 MHz, DMSO-d₆+one drop of 20% DCl in D₂O, δ_(H)):8.67 (s, 1H); 8.62-8.52 (m, 3H); 8.52-8.47 (m, 1H); 8.41-8.34 (m, 1H);3.94 (s, 2H).

LC-MS purity: 100% (ELSD), 100% (UV, 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.44 min.

LC-MS m/z: 534.3 (M+H)⁺.

Example 294-[(3R,4R)-3,4-bis[[1-hydroxy-4-(trifluoromethyl)-3H-2,1-benzoxaborole-6-carbonyl]amino]pyrrolidin-1-yl]-4-oxobutanoicacid

4-[(3R,4R)-3,4-bis[[1-hydroxy-4-(trifluoromethyl)-3H-2,1-benzoxaborole-6-carbonyl]amino]pyrrolidin-1-yl]-4-oxobutanoicacid was prepared similarly to the compound of Example 27 from4-((3R,4R)-3,4-bis((tert-butoxycarbonyl)amino)-pyrrolidin-1-yl)-4-oxobutanoicacid.

Example 302-((Bis(3-borono-5-(trifluoromethyl)phenyl)(oxo)-λ6-sulfanylidene)amino)aceticacid

2-((Bis(3-borono-5-(trifluoromethyl)phenyl)(oxo)-λ6-sulfanylidene)amino)aceticacid was synthesized according to the reaction scheme shown in Chem. 34and following the procedure described below.

A mixture of 1-iodo-3-(trifluoromethyl)-benzene (1, 5.44 g, 20.0 mmol),3-(trifluoromethyl)-benzenethiol (2, 4.28 g, 24.0 mmol), copper(I)iodide (380 mg, 2.00 mmol), potassium carbonate (6.63 g, 48.0 mmol) anddry 1,2-dimethoxyethane (40 mL) was heated at 80 C under argon for twodays. The reaction mixture was cooled to room temperature; diluted withethyl acetate (80 mL); filtered over Celite and evaporated to dryness.The residue was re-dissolved in ethyl acetate (300 mL); washed withwater (100 mL), 5% aqueous solution of sodium carbonate (2×100 mL) and 1M aqueous solution of hydrochloric acid (50 mL); dried over anhydroussodium sulfate and evaporated to dryness. The residue (contaminated withunwanted diaryl disulfide) was dissolved in acetic acid (80 mL). Zincpowder (7.00 g) was added and the mixture was heated at 60 C for 3hours; then it was cooled to room temperature, diluted with toluene (80mL), filtered over Celite and evaporated to dryness. The residue waspartitioned between toluene (300 mL) and water (150 mL). The phases wereseparated, and the organic one was washed with 1 M aqueous solution ofsodium hydroxide (2×200 mL) and brine (100 mL), dried over anhydroussodium sulfate and evaporated to dryness. The residue was subjected toflash column chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane) to afford bis(3-(trifluoromethyl)phenyl)sulfane (3) ascolorless liquid.

Yield: 4.01 g (62%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 95:5): 0.50.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.65-7.61 (m, 2H); 7.58-7.42(m, 6H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)) −62.90 (s).

LC-MS purity: 93% (UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 2.96 min.

LC-MS m/z: 323.4 (M+H)⁺.

(Diacetoxyiodo)benzene (9.82 g, 30.5 mmol) was added to a mixture ofbis(3-(trifluoromethyl)phenyl)sulfane (3, 3.93 g, 12.2 mmol) andammonium carbamate (1.90 g, 24.4 mmol) in methanol (24.4 mL). Theresulting pale yellow solution was stirred at room temperature for 3hours, and then it was evaporated to dryness in vacuo. A solution ofpotassium hydrogen carbonate (20 g) and sodium thiosulfate (20 g) inwater (200 mL) was added to the residue, followed by ethyl acetate (200mL). The phases were separated and the aqueous one was extracted withethyl acetate (3×100 mL). The organic fractions were combined, driedover anhydrous sodium sulfate and evaporated in vacuo. The residue waspurified by flash column chromatography (Silicagel 60, 0.040-0.063 mm;eluent: cyclohexane/ethyl acetate 99:1 to 70:30) to giveiminobis(3-(trifluoromethyl)phenyl)-λ⁶-sulfanone (4) as pale yellow oil.

Yield: 3.50 g (81%).

R_(F) (SiO₂, n-hexane/ethyl acetate 1:1): 0.50.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.37-8.34 (m, 2H); 8.29-8.24(m, 2H); 7.88-7.81 (m, 2H); 7.73-7.65 (m, 2H); 3.28 (bs, 1H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −62.78 (s).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 3.53 min.

LC-MS m/z: 354.4 (M+H)⁺.

Sodium hydride (60% dispersion in mineral oil, 310 mg, 7.75 mmol) wasadded to a solution of iminobis(3-(trifluoromethyl)phenyl)-λ⁶-sulfanone(4, 2.49 g, 7.05 mmol) in dry N,N-dimethylformamide (20 mL) and themixture was stirred at room temperature for 1 hour. tert-Butylbromoacetate (2.36 mL, 10.6 mmol) was added; the mixture was heated to60° C. and stirred at this temperature for 2.5 hours. The mixture wascooled to room temperature and partitioned between 10% aqueous solutionof sodium hydrogensulfate (300 mL) and ethyl acetate (600 mL). Separatedorganic layer was washed with water (3×200 mL) and brine (100 mL); driedover anhydrous sodium sulfate and evaporated in vacuo. The residue waspurified by flash column chromatography (Silicagel 60, 0.040-0.063 mm;eluent: cyclohexane/ethyl acetate 99:1 to 70:30) to yield tert-butyl2-((oxobis(3-(trifluoromethyl)phenyl)-λ⁶-sulfanylidene)amino)acetate (5)as white solid.

Yield: 2.94 g (89%).

R_(F) (SiO₂, n-hexane/ethyl acetate 1:1): 0.55.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.34 (s, 2H); 8.28 (d, J=7.9Hz, 2H); 7.83 (d, J=7.9 Hz, 2H); 7.67 (t, J=7.9, 2H); 3.77 (s, 2H); 1.48(s, 9H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)) −62.77 (s).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 4.62 min.

LC-MS m/z: 468.4 (M+H)⁺. tert-Butyl2-((oxobis(3-(trifluoromethyl)phenyl)-λ⁶-sulfanylidene)amino)acetate (5,501 mg, 1.07 mmol), bis(pinacolato)diboron (680 mg, 2.68 mmol),(1,5-cyclooctadiene)(methoxy)iridium(I) dimer (21.0 mg, 0.03 mmol) and4,4-di-tert-butyl-2,2-dipyridyl (20.0 mg, 0.08 mmol) were dissolved indegassed tetrahydrofuran (3 mL) under argon. The resulting mixture waswarmed to 60 C and heated at this temperature for 6 hours. The mixturewas evaporated to dryness; and the residue purified by quick flashcolumn chromatography (Silicagel 60, 0.040-0.063 mm; eluent:dichloromethane) to give tert-butyl2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)-λ⁶-sulfanylidene)amino)acetate(6) as off-white foam.

Yield: 748 mg (97%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.59 (s, 2H); 8.42 (s, 2H);8.21 (s, 2H); 3.76 (s, 2H); 1.51 (s, 9H); 1.36 (s, 12H); 1.35 (s, 12H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −62.59 (s).

LC-MS purity: 100% (ELSD). LC-MS Rt (Kinetex C18, 4.6 mm×50 mm,acetonitrile/water 85:15 to 100:0+0.1% FA): 1.32 min (M-2×pinacol), 1.65(M-pinacol), 5.11 min (M).

LC-MS m/z: 556.6 (M-2×pinacol+H)⁺. 638.8 (M-pinacol+H)⁺. 721.0 (M+H)⁺.

Trifluoroacetic acid (6 mL) was added to a solution of tert-butyl2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)-_6-sulfanylidene)amino)acetate(6, 735 mg, 1.02 mmol) in dichloromethane (2 mL) and the mixture wasstirred for 2 hours at room temperature. The mixture was evaporated todryness in vacuo, and the residue was evaporated from dichloromethane(5×10 mL) to afford2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)-λ⁶-sulfanylidene)amino)aceticacid (7) as off-white foam.

Yield: 678 mg (100%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.54 (s, 2H); 8.33 (s, 2H);8.27 (s, 2H); 3.85 (s, 2H); 1.37 (s, 12H); 1.37 (s, 12H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)) −62.68 (s).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 85:15 to100:0+0.1% FA): 0.67 min (M-2×pinacol), 0.84 (M-pinacol), 2.04 min (M).

LC-MS m/z: 550.5 (M-2×pinacol+H)⁺, 582.7 (M-pinacol+H)⁺, 664.8 (M+H)⁺.

A solution of2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)-26-sulfanylidene)amino)aceticacid (7, 568 mg, 856 μmol) in acetonitrile (6 mL) was diluted with water(2.4 mL) followed by addition of periodic acid (780 mg, 3.42 mmol). Theresulting mixture was stirred for 1 hour; and then it was partitionedbetween ethyl acetate (120 mL) and water (30 mL). The phases wereseparated; the organic one was washed with brine (2×30 mL); dried overanhydrous sodium sulfate and evaporated to dryness. The residue wasdissolved in 0.5 M aqueous solution of sodium hydroxide (30 mL) andwashed with dichloromethane (3×40 mL). The aqueous layer was acidifiedwith 1 M aqueous solution of hydrochloric acid (30 mL) and extractedwith ethyl acetate (2×60 mL). Ethyl acetate extracts were combined,dried over anhydrous sodium sulfate and concentrated in vacuo until theproduct started to precipitate (approx. 10 mL volume). The suspensionwas diluted with n-hexane (50 mL) and placed into a freezer for 30minutes. The precipitate was collected by filtration, washed withn-hexane (3×5 mL), dried in vacuo and dissolved in 50% aqueousacetonitrile (60 mL). The resulting solution was freeze-dried to affordthe title compound (8) as white powder.

Yield: 338 mg (79%).

¹H NMR spectrum (300 MHz, DMSO-d₆+DCl, δ_(H)): 8.60 (s, 2H); 8.35 (s,4H); 3.70 (s, 2H).

¹⁹F NMR spectrum (282 MHz, DMSO-d₆+DCl, δ_(F)): −61.24 (s).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.89 min.

LC-MS m/z: 500.5 (M+H)⁺.

Example 31N-(4-(Difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine

N-(4-(Difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycinewas synthesized according to the reaction scheme shown in Chem. 35 andfollowing the procedure described below.

N-Iodosuccinimide (NIS, 61.5 g, 274 mmol) was added to a solution of3-bromo-4-methylbenzoic acid (1, 56.0 g, 260 mmol) in concentratedsulfuric acid (1 L) and the reaction mixture was allowed to stir atambient temperature for 16 hours. The reaction mixture was then pouredinto ice-water (2 L). Resulting mixture was poured onto ice bath (2 L),precipitate was filtered, washed with water and dried in vacuo toprovide 3-bromo-5-iodo-4-methylbenzoic acid (2) as off-white solid.

Yield: 87.8 g (99%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 8.30 (d, J=1.7 Hz, 1H); 8.06(d, J=1.7 Hz, 1H); 2.64 (s, 3H).

Concentrated sulfuric acid (25 mL) was added to a solution of3-bromo-5-iodo-4-methylbenzoic acid (2, 30.0 g, 88.0 mmol) in methanol(1 L) and the reaction mixture was allowed to stir under refluxovernight. The reaction mixture was then evaporated under reducedpressure, dissolved in diethyl ether (500 mL), washed with water (2×200mL) and saturated solution of potassium carbonate (200 mL). Organiclayer was separated, dried over anhydrous sodium sulfate, filtered andevaporated to provide methyl 3-bromo-5-iodo-4-methylbenzoate (3) aswhite solid.

Yield: 26.1 g (84%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 8.32 (d, J=1.7 Hz, 1H); 8.09(d, J=1.3 Hz, 1H); 3.86 (s, 3H); 2.65 (s, 3H).

To a solution of methyl 3-bromo-5-iodo-4-methylbenzoate (3, 9.00 g, 25.4mmol) in dry tetrahydrofuran (250 mL) 1.3 M solution ofisopropylmagnesium chloride lithium chloride complex in tetrahydrofuran(21.6 mL, 28.0 mmol) was added dropwise at −30 C under inert atmosphereand was stirred for 20 minutes. Then N,N-dimethylformamide (3.60 mL,38.1 mmol) was added at −30 C. The reaction mixture was allowed to warmto ambient temperature and stirred for 16 hours. The reaction mixturewas then evaporated under reduced pressure, dissolved in ethyl acetate(200 mL) and washed with water (2×100 mL). Organic layer was separated,dried over anhydrous sodium sulfate, filtered and evaporated to providemethyl 3-bromo-5-formyl-4-methylbenzoate (4) as white solid.

Yield: 6.24 g (96%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 10.27 (s, 1H); 8.53-8.34 (m,2H); 3.97 (s, 3H); 2.82 (s, 3H).

Solution of 3-bromo-5-formyl-4-methylbenzoate (4, 6.23 g, 24.3 mmol) and(diethylamino)sulfur trifluoride (DAST, 6.40 mL, 48.5 mmol) indichloromethane (150 mL) was stirred at ambient temperature for 16hours. Reaction was quenched by addition of water (75 mL) and extractedwith dichloromethane (2×100 mL). Organic layers were combined, driedover anhydrous sodium sulfate, filtered and evaporated to provide methyl3-bromo-5-(difluoromethyl)-4-methylbenzoate (5) as white solid.

Yield: 6.53 g (96%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.35 (d, J=1.1 Hz, 1H); 8.14(d, J=0.9 Hz, 1H); 6.78 (t, J=54.8 Hz, 1H); 3.93 (s, 3H); 2.55 (t, J=1.4Hz, 3H).

Solution of 1-bromopyrrolidine-2,5-dione (NBS, 4.57 g, 25.7 mmol),methyl 3-bromo-5-(difluoromethyl)-4-methylbenzoate (5, 6.53 g, 23.4mmol) and 2,2-azobis(2-methylpropionitrile) (AIBN, 192 mg, 1.17 mmol) inPhCF₃ (200 mL) was stirred overnight at 85 C. Reaction mixture wasevaporated and then extracted with diethyl ether (2×200 mL). Organiclayers were washed with brine (150 mL). Organic layer was separated,dried over anhydrous sodium sulfate, filtered and evaporated. The crudeproduct 6 was stirred with potassium acetate (4.59 g, 46.8 mmol) inacetonitrile (200 mL) at 75 C overnight. The suspension was filteredthrough filtering paper and evaporated. The crude product was dissolvedin dichloromethane and filtered again. The filtrate was evaporated andpurified by column chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/ethyl acetate 7:1) to give methyl4-(acetoxymethyl)-3-bromo-5-(difluoromethyl)benzoate (7) as white solid.

Yield: 4.24 g (54%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.40 (s, 1H); 8.26 (s, 1H);7.02 (t, J=54.7 Hz, 1H); 5.38 (s, 2H); 3.97 (s, 3H); 2.11 (s, 3H).Solution of methyl 4-(acetoxymethyl)-3-bromo-5-(difluoromethyl)benzoate(7, 4.24 g, 12.6 mmol), bis(pinacolato)diboron (3.52 g, 13.9 mmol),potassium acetate (3.70 g, 37.8 mmol) and[1,1-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (513 mg, 0.63mmol) in dry tetrahydrofuran (100 mL) was allowed to stir at 75 C underargon atmosphere for 10 days. Then the reaction mixture was cooled toambient temperature, filtered and evaporated. The crude product wasfiltered through silica gel column (Silicagel, 0.063-0.200 mm; eluent:cyclohexane/ethyl acetate 9:1) to provide methyl4-(acetoxymethyl)-3-(difluoromethyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(8).

Yield: 2.82 g (53%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 9:1): 0.40.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.57 (s, 1H); 8.38 (s, 1H);7.04 (t, J=55.1 Hz, 1H); 5.54 (s, 2H); 3.97 (s, 3H); 2.06 (s, 3H); 1.39(s, 12H).

Solution of methyl4-(acetoxymethyl)-3-(difluoromethyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(8, 2.82 g, 7.34 mmol) and sodium hydroxide (1.47 g, 36.7 mmol) in water(50 mL) was stirred at ambient temperature for 3 hours. Then solution ofconcentrated hydrochloric acid (4 mL) in water (10 mL) was added tolower the pH to 1. The reaction mixture was left in the fridgeovernight. Precipitate was filtered and dried to provide4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (9) as white solid.

Yield: 1.32 g (79%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 13.25 (bs, 1H); 9.54 (s, 1H);8.51 (s, 1H); 8.20 (s, 1H); 7.22 (t, J=55.1 Hz, 1H); 5.19 (s, 2H).

Solution of 2,3,4,5,6-pentafluorophenol (242 mg, 1.32 mmol),4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (9, 300 mg, 1.32 mmol) and N,N′-dicyclohexylcarbodiimide (DCC, 272mg, 1.32 mmol) in acetonitrile (20 mL) was stirred at ambienttemperature overnight. The reaction mixture was filtered, evaporated,dissolved in acetonitrile, re-filtered and evaporated to give theperfluorophenyl4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(10) as white solid.

Yield: 520 mg (100%).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 4.65 min.

LC-MS m/z: 395.5 (M+H)⁺.

Solution of the perfluorophenyl4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(10, 520 mg, 1.32 mmol), (2-aminoethyl)glycine (11, 78.0 mg, 0.66 mmol)and triethylamine (1.84 mL, 6.60 mmol) in N,N-dimethylformamide (10 mL)was stirred at ambient temperature for 3 days. The reaction mixture wasthen evaporated and crude product 12 was purified by preparative HPLC(SunFire Prep C18 OBD, 5 m, 19×100 mm, acetonitrile/water 5:95 to100:0+0.1% FA) and freeze-dried to affordN-(4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine(12) as white solid.

Yield: 110 mg (31%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.89 (bs, 1H); 9.63-9.35 (m,2H); 8.92-6.70 (m, 7H); 5.25-5.08 (m, 4H); 4.28-3.94 (m, 2H); 3.74-3.35(m, 4H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.30 min.

LC-MS m/z: 539.4 (M+H)⁺.

Example 32N-(4-Chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine

N-(4-Chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycinewas synthesized according to the reaction scheme shown in Chem. 36 andfollowing the procedure described below.

Concentrated sulfuric acid (4.00 mL, 73.3 mmol) was added to a solutionof 3-chloro-4-methylbenzoic acid (1, 25.0 g, 147 mmol) in methanol (200mL) and the reaction mixture was allowed to stir at 60 C for 2 days. Thesolution was cooled to room temperature, sodium hydrogencarbonate (6.80g, 80.0 mmol) was added, and the mixture was evaporated under reducedpressure. The residue was partitioned between ethyl acetate (300 mL) andwater (250 mL). The organic layer was separated; washed with 0.5 Maqueous solution of sodium hydroxide (2×250 mL), 0.5 M aqueous solutionof hydrochloric acid (200 mL) and brine (150 mL); dried over anhydroussodium sulfate and evaporated in vacuo to give methyl3-chloro-4-methylbenzoate (2) as orange oil.

Yield: 27.0 g (98%).

RE (SiO₂, dichlormethane/methanol 95:5): 0.80.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)) 8.00 (d, J=1.65 Hz, 1H); 7.80(dd, J=7.9 and 1.5 Hz, 1H); 7.28 (d, J=8.1 Hz, 1H); 3.90 (s, 3H); 2.42(s, 3H).

Methyl 3-chloro-4-methylbenzoate (2, 26.0 g, 141 mmol) was dissolved insulfuric acid (150 mL) followed by addition of N-iodosuccinimide (38.0g, 169 mmol). The resulting mixture was stirred overnight at roomtemperature then it was poured onto ice. When ice was completely meltedthe mixture was extracted with ethyl acetate (300 mL). Organic layer waswashed with 5% aqueous solution of sodium thiosulfate (3×100 mL) andwater (1×100 mL), dried over anhydrous sodium sulfate, filtered andevaporated to dryness. Product was re-crystallized from hot heptane (150mL) affording methyl 3-chloro-5-iodo-4-methylbenzoate (3) as whitepowder.

Yield: 32.0 g (73%).

R_(F) (SiO₂, dichlormethane/methanol 95:5): 0.80.

¹H NMR spectrum (300 MHz, DMSO-d₆: δ_(H)): 8.38 (dd, J=1.3 Hz, 1H); 8.00(dd, J=1.3 Hz, 1H); 3.87 (s, 3H); 2.54 (s, 3H).

A stirred mixture of methyl 3-chloro-4-methylbenzoate (3, 30.0 g, 96.6mmol), 1-bromopyrrolidine-2,5-dione (NBS, 18.9 g, 106 mmol) and water(400 mL) in a wide beaker was placed under D3 basking lamp for reptiles(100 W, UVA, UVB, IR) and heated to 90-100° C. from suspension to oilyconsistency. Another portion of 1-bromopyrrolidine-2,5-dione (0.00 g,11.3 mmol) was added after 6 hours, and the mixture was stirred for anadditional 5 hours. The mixture was cooled to room temperature followedby extraction with ethyl acetate (3×200 mL). Combined organic layerswere washed with 5% aqueous solution of sodium thiosulfate (3×100 mL),water (1×100 mL), brine (1×100 mL), dried over anhydrous sodium sulfateand evaporated in vacuo to afford crude methyl4-(bromomethyl)-3-chloro-5-iodobenzoate (4) as yellow solid.

Yield: 29.5 g (78%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 8:2): 0.70.

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 8.80 (s, 1H); 8.41 (s, 1H);4.81 (s, 2H); 3.94 (s, 3H).

A mixture of the above crude methyl4-(bromomethyl)-3-chloro-5-iodobenzoate (4, 28.0 g, 71.9 mmol) andpotassium acetate (21.2 g, 216 mmol) in acetonitrile (600 mL) was heatedat 80 C for 7 hours. The mixture was cooled to room temperature, thesolid was removed by filtration and washed with ethyl acetate (3×50 mL).The filtrate was evaporated to dryness, and the residue was partitionedbetween ethyl acetate (500 mL) and water (200 mL). The organic layer wasseparated, washed with water (200 mL) and brine (2×200 mL), dried overanhydrous sodium sulfate and evaporated in vacuo. The residue waspurified by flash column chromatography (Silicagel, 0.063-0.200 mm;eluent: cyclohexane/ethyl acetate 97:3) and after was recrystallizedfrom hot cyclohexane to give pure methyl4-(acetoxymethyl)-3-chloro-5-iodobenzoate (5) as white solid.

Yield: 19.3 g (62%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 4:1): 0.60.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.42 (d, J=3.3 Hz, 1H); 8.04(d, J=3.6 Hz, 1H); 5.40 (s, 2H); 3.94 (s, 3H); 2.12 (s, 3H).

LC-MS purity: 100% (UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 50:50 to100:0+0.1% FA): 2.62 min.

LC-MS m/z: 369.5 (M+H)⁺.

[1,1-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (2.48 g, 3.39mmol) was added to a degassed solution of methyl4-(acetoxymethyl)-3-chloro-5-iodobenzoate (5, 25.0 g, 63.8 mmol),bis(pinacolato)diboron (19.0 g, 74.6 mmol) and potassium acetate (20.0g, 204 mmol) in dry 1,4-dioxane (300 mL) under argon. The mixture waswarmed to 80 C and stirred at this temperature for 3 days. The mixturewas cooled to room temperature; then it was diluted with dichloromethane(200 mL) and passed through a short column of silicagel topped withCelite followed by elution with dichloromethane. Fractions containingthe product were combined and evaporated to dryness. The residue waspurified by flash column chromatography (Silicagel, 0.063-0.200 mm;eluent: cyclohexane/ethyl acetate 9:1 to 7:3) to affording methyl4-(acetoxymethyl)-3-chloro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(6) yellow oil.

Yield: 25.0 g (100%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 8:2): 0.4.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.34 (d, J=1.65 Hz, 1H); 8.12(d, J=8.2 and 2.0 Hz, 1H); 5.52 (s, 2H); 3.93 (s, 3H); 2.05 (s, 3H);1.34 (s, 12H).

LC-MS purity: 100% (ELSD), 88% (UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 50:50 to100:0+0.1% FA): 3.54 min. LC-MS m/z: 369.6 (M+H)⁺.

Methyl4-(acetoxymethyl)-3-chloro-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(6, 25.0 g, <63.8 mmol) was added to a solution of sodium hydroxide(12.8 g, 319 mmol) in water (300 mL) and the resulting mixture wasstirred at room temperature for 5 hours. The mixture was filtered andacidified with 35% hydrochloric acid (39.6 mL, 444 mmol). The resultingwhite suspension was stirred for another one hour. The precipitate wasfiltered, washed with water (5×50 mL) and dissolved in 80% aqueoussolution of acetonitrile (500 mL), filtered and solution mixture wasfreeze-dried to afford4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid(7) as white powder.

Yield: 9.00 g (63%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 13.30 (s, 1H); 9.60 (s, 1H);8.32 (d, J=1.1 Hz, 1H); 8.00 (d, J=1.1 Hz, 1H); 5.06 (s, 2H).

LC-MS purity: 99% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.90 min.

LC-MS m/z: 213.3 (M+H)⁺.

N-(3-Dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (3.40 g,17.9 mmol) was added to a suspension of4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid(7, 3.80 g, 17.9 mmol) and pentafluorophenol (3.30 g, 17.9 mmol) insolution acetonitrile/dichloromethane (1:1, 150 mL) and the mixture wasstirred at room temperature overnight. Solvent was evaporated todryness. Residue was partionated between ethyl acetate (200 mL) and 10%aqueous solution of potassium hydrogensulfate (200 mL). Organic layerwas separate and washed with water (2×100 mL), dried over anhydroussodium sulfate and evaporated in vacuo. Residue dissolved indichloro-methane placed in the fridge overnight. The solid was filteredoff and washed with ethyl acetate (2×20 mL). The filtrates were combinedand evaporated to dryness. Cyclohexane (100 mL) was added to the residueand the mixture was stirred at room temperature for 15 minutes. Themixture was decanted and the sediment was dried in vacuo to giveperfluorophenyl4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (8)as off-white solid.

Yield: 4.80 g (71%).

LC-MS purity: 98% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 4.48 min.

LC-MS m/z: 379.4 (M+H)⁺.

N,N-Diisopropylethylamine (2.35 mL, 13.5 mmol) was added to a mixture ofperfluorophenyl1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (9, 1.40 g,3.72 mmol) and L-2,3-diaminopropionic acid hydrochloride (9,N-2-aminoethylglycine, 200 mg, 1.70 mmol) in solutionN,N-dimethylformamide/water (4:1, 20 mL) and the resulting solution wasstirred at room temperature overnight. The mixture was evaporated todryness in vacuo, and the residue was partitioned between 1 M aqueoussolution of hydrochloric acid (40 mL) and ethyl acetate (50 mL). Thephases were separated and the organic one was extracted with ethylacetate (2×25 mL). All organic layers was combined, dried over anhydroussodium sulfate and concentrated in vacuo. Mixture was evaporated withtoluene three time. Dichloromethane (50 mL) was added and the resultingsuspension was stirred at room temperature 2 hours. Solid was decantedand all was repeat another one. The precipitate was triturated with amixture of dichloro-methane/methanol/formic acid (1000:20:3), the solidwas collected by filtration, washed with cyclohexane (2×5 mL) andair-dried to give title compound (10) as white powder.

Yield: 180 mg (21%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.87 (bs, 1H); 9.67-9.37 (m,1H); 8.87-7.09 (m, 5H); 5.15-4.86 (m, 4H); 4.34-3.92 (m, 2H); 3.60-3.24(m, 4H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 2.58 min.

LC-MS m/z: 507.3 (M+H)⁺.

Example 33(S)-3-(2,3-Bis(4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanamido)propanoicacid

(S)-3-(2,3-Bis(4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanamido)propanoicacid was synthesized according to the reaction scheme shown in Chem. 37and following the procedure described below.

2-Chlorotrityl chloride resin 100-200 mesh 1.5 mmol/g (3.30 g, 4.95mmol) was left to swell in dry dichloromethane (300 mL) for 30 minutes.A solution of 3-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)propanoicacid (1, Fmoc-beta-Ala-OH, 0.50 g, 1.60 mmol) in dry dichloromethane(100 mL) and N,N-diisopropylethylamine (2.00 mL, 15.5 mmol) was addedand the mixture was shaken overnight. Then resin was filtered andtreated with a solution ofN,N-diisopropylethylamine/methanol/dichloromethane mixture (1:2:8, 2×5min, 2×50 mL). The resin was washed with dichloromethane (3×100 mL),2-propanol (3×100 mL) and N,N-dimethylformamide (3×100 mL). Fmoc groupwas removed by treatment with 20% piperidine in N,N-dimethylformamide(1×5 min, 1×30 min, 2×100 mL). Resin was washed withN,N-dimethylformamide (3×100 mL), 2-propanol (3×100 mL) anddichloromethane (3×100 mL). A solution of(S)-2,3-bis((((8a9H-fluoren-9-yl)methoxy)carbonyl)amino)propanoic acid(2, Fmoc-Dap(Fmoc)-OH, 1.00 g, 1.82 mmol) and N,N-diisopropylethylamine(3.00 mL, 4.04 mmol) in dichloromethane (100 mL) was added to resin andmixture was shaken for 5 hours. Resin was filtered and washed withdichloromethane (3×100 mL), 2-propanol (3×100 mL) and dichloromethane(3×100 mL). Fmoc groups were removed by treatment with 20% piperidine inN,N-dimethylformamide (1×5 min, 1×30 min, 2×100 mL). Resin was washedwith dichloromethane (3×100 mL), 2-propanol (3×100 mL) anddichloro-methane (3×100 mL). A solution of pentafluorophenyl1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (3, 1.40 g,3.72 mmol; #8 in example above) and N,N-diisopropylethylamine (6.00 mL,60.0 mmol) in N,N-dimethylformamide (50 mL) was added to resin andmixture was shaken for 5 hours. The resin was washed withdichloromethane (3×100 mL), 2-propanol (3×100 mL), N,N-dimethylformamide(3×100 mL) and dichloromethane (5×100 mL).

The product was cleaved from resin by treatment with1,1,1,3,3,3-hexafluoroisopropanol in dichloromethane (3:1, 100 mL).Resin was filtered and washed with dichloromethane (3×100 mL). Solutionswere combined and solvents were evaporated to dryness to give crudemixture was subjected to purification by preparative LC/MS (SunFire PrepC18 OBD, 5m, 19×100 mm, acetonitrile/water 5:95 to 100:0+0.1% FA). Purefractions were combined and freeze-dried to give title compound (4) aswhite powder.

Yield: 103 mg (11%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.16 (bs, 1H); 9.54 (d,J=6.24 Hz, 2H); 8.74-8.63 (m, 2H); 8.19 (d, J=1.1 Hz, 1H); 8.15-8.08 (m,2H); 8.02 (d, J=1.28 Hz, 1H); 7.09 (d, J=1.1 Hz, 1H); 5.03 (d, J=7.34Hz, 4H); 4.71-4.61 (m, 1H); 3.59 (t, J=5.59 Hz, 2H); 3.30-3.23 (m, 2H);2.37 (t, J=7.15 Hz, 2H).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.63 min.

LC-MS m/z: 563.0 (M+H)⁺.

Example 342-((Bis(3-borono-5-(difluoromethyl)phenyl)(oxo)-λ6-sulfanylidene)amino)aceticacid

2-((Bis(3-borono-5-(difluoromethyl)phenyl)(oxo)-λ6-sulfanylidene)amino)aceticacid was synthesized according to the reaction scheme shown in Chem. 38and following the procedure described below.

The mixture of 3-iodobenzaldehyde (1, 4.00 g, 17.2 mmol) in Deoxo-Fluor(12 mL) was stirred at room temperature overnight. Then it was dilutedwith dichloromethane (150 mL) followed by dropwise addition of 10%aqueous solution of potassium carbonate (200 mL) at 0 C. Phases wereseparated; organic layer was dried over anhydrous sodium sulfate,filtered and evaporated. The residue was subjected to flash columnchromatography (Silicagel 60, 0.040-0.063 mm; eluent: cyclohexane) toafford 1-(difluoromethyl)-3-iodobenzene (2) as colorless oil.

Yield: 3.22 g (74%).

R_(F) (SiO₂, cyclohexane): 0.50.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.89-7.85 (m, 1H); 7.85-7.79(m, 1H); 7.52-7.46 (m, 1H); 7.24-7.17 (m, 1H); 6.59 (t, J=56.2 Hz, 1H).

Iodide (2, 1.48 g, 5.81 mmol) was dissolved in dry tetrahydrofuran (20mL) under nitrogen atmosphere and cooled down to −30 C. 1.3 M Solutionof isopropylmagnesium chloride lithium chloride complex intetrahydrofuran (4.69 mL, 6.10 mmol) was added dropwise. Resultingsolution was stirred for 1.5 hours at −30 C. Then a solution ofbis(phenylsulfonyl)sulfide (0.82 g, 2.61 mmol) in degassedtetrahydrofuran (10 mL) was added. The mixture was left to warm up toroom temperature (approx. 2 hours). The reaction was quenched byaddition of 20% aqueous solution of ammonium chloride (30 mL) andextracted with diethyl ether (50 mL). Organic layer was washed withwater (3×50 mL) and brine (1×50 mL), dried over anhydrous sodiumsulfate, filtered and evaporated. The residue was subjected to flashcolumn chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane) to afford bis(3-(difluoromethyl)phenyl)sulfane (3) ascolorless oil which crystallized in fridge.

Yield: 568 mg (76%).

R_(F) (SiO₂, cyclohexane): 0.20.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.52-7.48 (m, 2H); 7.48-7.37(m, 6H); 6.61 (t, J=56.3 Hz, 2H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)) −111.21 (s); −111.40 (s).(Diacetoxyiodo)benzene (966 mg, 3.00 mmol) was added to a mixture ofsulfide (3, 343 mg, 1.20 mmol) and ammonium carbamate (187 mg, 2.40mmol) in methanol (5.5 mL).

The resulting pale yellow solution was stirred at room temperature for 3hours, and then it was evaporated to dryness in vacuo. A solution ofpotassium hydrogen carbonate (2 g) and sodium thiosulfate (2 g) in water(20 mL) was added to the residue, followed by ethyl acetate (70 mL). Thephases were separated and the aqueous one was extracted with ethylacetate (2×70 mL). The organic fractions were combined, dried overanhydrous sodium sulfate and evaporated in vacuo. The residue waspurified by flash column chromatography (Silicagel 60, 0.040-0.063 mm;eluent: cyclohexane/ethyl acetate 2:1) to affordbis(3-(difluoromethyl)phenyl)(imino)-λ⁶-sulfanone (4) as white solid.

Yield: 553 mg (89%).

R_(F) (SiO₂, n-hexane/ethyl acetate 1:1): 0.45.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.24-8.12 (m, 4H); 7.75-7.68(m, 2H); 7.68-7.58 (m, 2H); 6.70 (t, J=56.0 Hz, 2H); 3.20 (bs, 1H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −111.74 (s); −111.94 (s).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 2.70 min.

LC-MS m/z: 317.3 (M+H)⁺.

60% Sodium hydride dispersion in mineral oil (0.08 g, 1.88 mmol) wasadded to a solution of the above compound (4, 543 mg, 1.71 mmol) in dryN,Ndimethylformamide (5 mL) and the mixture was stirred at roomtemperature for 1 hour. tert-Butyl bromoacetate (0.38 mL, 2.57 mmol) wasadded; the mixture was heated to 60 C and stirred at this temperaturefor 2.5 hours. The mixture was cooled to room temperature andpartitioned between 10% aqueous solution of sodium hydrogensulfate (30mL) and ethyl acetate (60 mL). Separated organic layer was washed withwater (3×30 mL), dried over anhydrous sodium sulfate and evaporated invacuo. The residue was purified by flash column chromatography(Silicagel 60, 0.040-0.063 mm; eluent: cyclohexane/ethyl acetate 4:1) toyield tert-butyl2-((bis(3-(difluoromethyl)phenyl)(oxo)-λ⁶-sulfanylidene)amino)acetate(5) as colorless oil.

Yield: 708 mg (96%).

R_(F) (SiO₂, n-hexane/ethyl acetate 1:1): 0.65.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.23-8.16 (m, 4H); 7.75-7.70(m, 2H); 7.67-7.58 (m, 2H); 6.69 (t, J=56.0 Hz, 2H); 3.76 (s, 2H); 1.47(s, 9H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)) −111.56 (s); −111.76 (s).

The above prepared compound (5, 700 mg, 1.62 mmol),bis(pinacolato)diboron (1.03 g, 4.05 mmol),(1,5-cyclooctadiene)(methoxy)iridium(I) dimer (33.0 mg, 0.05 mmol) and4,4-di-tert-butyl-2,2-dipyridyl (dtbpy, 30.0 mg, 0.11 mmol) weredissolved in degassed tetrahydrofuran (16 mL) under nitrogen. Theresulting mixture was warmed to 50 C and heated at this temperatureovernight. The mixture was evaporated to dryness; and the residuepurified by quick flash column chromatography (Silicagel 60, 0.040-0.063mm; eluent: dichloromethane) to give tert-butyl2-((bis(3-(difluoromethyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)(oxo)-λ⁶-sulfanylidene)amino)acetate(6) as beige foam.

Yield: 945 mg (85%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.53 (s, 2H); 8.30 (s, 2H);8.11 (s, 4H); 6.69 (t, J=56.0 Hz, 2H); 3.75 (s, 2H); 1.51 (s, 9H); 1.35(s, 12H); 1.35 (s, 12H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −111.26 (s); −111.49 (s).

Trifluoroacetic acid (20 mL) was added to a solution of the abovecompound (6, 935 mg, 1.04 mmol) in dichloromethane (4 mL) and themixture was stirred for 2 hours at room temperature. The mixture wasevaporated to dryness in vacuo, and the residue was evaporated fromdichloromethane (5×10 mL) to afford2-((bis(3-(difluoromethyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)(oxo)-λ⁶-sulfanylidene)amino)aceticacid (7) as beige foam.

Yield: 858 mg (100%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.49 s, 2H); 8.22 (s, 2H); 8.18(s, 2H); 6.72 (t, J=55.8 Hz, 2H); 3.88 (s, 2H); 1.37 (s, 12H); 1.37 (s,12H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −111.84 (s); −112.03 (s).

A solution of the acid (7, 858 mg, 1.37 mmol) in acetonitrile (16 mL)was diluted with water (4 mL) followed by addition of periodic acid(1.25 g, 5.48 mmol). The resulting mixture was stirred for 1 hour; andthen it was partitioned between ethyl acetate (120 mL) and water (30mL). The phases were separated; the organic one was washed with water(1×60 mL); dried over anhydrous sodium sulfate and evaporated todryness. The residue was dissolved in 0.5 M aqueous solution of sodiumhydroxide (50 mL) and washed with dichloromethane (2×80 mL). The aqueouslayer was acidified with 1 M aqueous solution of hydrochloric acid (80mL) and extracted with ethyl acetate (3×120 mL). Ethyl acetate extractswere combined, dried over anhydrous sodium sulfate, filtered andevaporated. Part of the residual material (0.20 g) was purified bypreparative LC/MS (SunFire Prep C18 OBD, 5m, 19×100 mm,acetonitrile/water 5:95 to 100:0+0.1% FA) to give title compound (8) aswhite powder.

Yield: 170 mg (85%).

¹H NMR spectrum (300 MHz, DMSO-d₆+DCl, δ_(H)): 8.48 (s, 2H); 8.19 (s,4H); 7.14 (t, J=55.6 Hz, 2H); 3.65 (s, 2H).

¹⁹F NMR spectrum (282 MHz, DMSO-d₆+DCl, δ_(F)): −110.64 (s); −110.84(s).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.27 min.

LC-MS m/z: 462.9 (M+H)⁺.

Example 352-((Bis(3-borono-5-chlorophenyl)(oxo)-λ6-sulfanylidene)amino)acetic acid

2-((Bis(3-borono-5-chlorophenyl)(oxo)-λ6-sulfanylidene)amino)acetic acidwas synthesized according to the reaction scheme shown in Chem. 39 andfollowing the procedure described below.

A well stirred suspension of 3-chloroiodobenzene (1, 10.2 g, 42.6 mmol),sodium sulfide nonahydrate (7.16 g, 29.8 mmol), potassium carbonate(5.89 g, 42.6 mmol) and copper(I) iodide (811 mg, 4.26 mmol) in dryN,N-dimethylformamide (85 mL) was heated to 120° C. (oil bath) for 72hours. After cooling to ambient temperature, the reaction mixture wasdiluted with diethyl ether (150 mL) and filtered through a pad ofCelite, the pad was washed with more diethyl ether (3×100 mL). Thefiltrate was transferred to a separatory funnel and washed with water(200 mL) and 1 M aqueous solution of sodium hydroxide (2×150 mL). Theorganic layer was dried over anhydrous sodium sulfate, filtered andevaporated. The residue was subjected to flash column chromatography(Silicagel 60, 0.063-0.200 mm; eluent: cyclohexane) to givebis(3-chlorophenyl)sulfane (2) as colorless oil.

Yield: 4.66 g (86%).

¹H NMR spectrum (300 MHz, DMSO-d₆, 6H): 7.45-7.38 (m, 6H); 7.35-7.29 (m,2H). LC-MS purity: 97% (UV 254).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 3.25 min.

LC-MS m/z: 254.1 (M+H)⁺.

To a well-stirred solution of bis(3-chlorophenyl)sulfane (2, 4.00 g,15.7 mmol) in methanol (37 mL) was added ammonium carbamate (2.84 g,31.4 mmol) and bis(acetoxy)iodobenzene (14.7 g, 39.3 mmol). After 2hours, the reaction mixture was evaporated in vacuo and the residue wasdissolved in ethyl acetate (40 mL) and washed with 10% aqueous solutionof sodium thiosulfate (40 mL), 10% aqueous solution of potassiumbicarbonate (40 mL) and brine (40 mL). The organic layer was separated,dried over anhydrous sodium sulfate, filtered and evaporated. Theresidue was subjected to flash column chromatography (Silicagel 60,0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 3:1) to givebis(3-chlorophenyl)(imino)-λ⁶-sulfanone (3) as yellowish oil.

Yield: 4.13 g (94%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)) 8.03 (t, J=1.8 Hz, 2H);7.95-7.88 (m, 2H); 7.55-7.49 (m, 2H); 7.44 (t, J=7.9 Hz, 2H); 3.15 (bs,1H).

LC-MS purity: 100% (ELSD, UV 242).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 40:60 to100:0+0.1% FA): 2.65 min.

LC-MS m/z: 286.2 (M+H)⁺.

To an ice-cold, well-stirred solution ofbis(3-chlorophenyl)(imino)-λ⁶-sulfanone (3, 4.13 g, 16.2 mmol) inanhydrous N,N-dimethylformamide (45 mL) was added sodium hydride (712mg, 17.8 mmol) under nitrogen. After 5 minutes, tert-butyl bromoacetate(4.74 mL, 24.3 mmol) was added. The reaction mixture was allowed toreach ambient temperature and stirred for an hour. The reaction mixturewas then taken up in ethyl acetate (160 mL) and washed with 10% aqueoussolution of ammonium chloride (160 mL), water (2×160 mL) and brine (160mL). The organic layer was dried over anhydrous sodium sulfate, filteredand evaporated. The crude product was purified by column chromatography(Silicagel, 0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 20:1 to3:1) to provide tert-butyl2-((bis(3-chlorophenyl)(oxo)-λ⁶-sulfanylidene)amino)acetate (4) asyellowish oil.

Yield: 4.73 g (76%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.04 (t, J=1.8 Hz, 2H); 7.94(dt, J=7.7, 1.4 Hz and 2H); 7.55-7.49 (m, 2H); 7.44 (t, J=7.9 Hz, 2H);3.76 (s, 2H); 1.48 (s, 9H).

LC-MS purity: 100% (ELSD, UV 242).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 40:60 to100:0+0.1% FA): 4.29 min.

LC-MS m/z: 400.3 (M+H)⁺. tert-Butyl2-((bis(3-chlorophenyl)(oxo)-λ⁶-sulfanylidene)amino)acetate (4, 400 mg,1.00 mmol), bis(pinacolato)diboron (635 mg, 2.50 mmol),(1,5-cyclooctadiene)(methoxy)iridium(I) dimer (26.5 mg, 0.04 mmol) and4,4′-di-tert-butyl-2,2′-dipyridyl (dtbpy, 26.5 mg, 0.04 mmol) weredissolved in dry, degassed tetrahydrofuran (4 mL) under nitrogen. Thereaction mixture was stirred at 60° C. (oil bath) for 16 hours.Afterwards, the reaction mixture was evaporated to dryness and theresidue was dissolved in dichloromethane (10 mL) and filtered through aplug of silicagel (7.00 g) topped with Celite with the aid ofdichloromethane (4×15 mL). The filtrate was evaporated to give crudetert-butyl2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)-λ⁶-sulfanylidene)amino)acetate(5) as yellowish foam.

It was dissolved in acetonitrile (6 mL) and water (2 mL) and periodicacid (1596 mg, 7.00 mmol) was added. The resulting mixture was stirredfor 1 hour and it was then partitioned between ethyl acetate (30 mL) andwater (30 mL). The phases were separated and the organic layer waswashed with brine (2×30 mL), dried over anhydrous sodium sulfate,filtered and evaporated to give a yellowish waxy solid.

The solid was dissolved in trifluoroacetic acid (5 mL) and the mixturewas stirred for 1 hour at room temperature. The mixture was evaporatedto dryness in vacuo, and the residue was co-distilled with ethyl acetate(5×10 mL) and acetonitrile (5×5 mL). A part of the residue was dissolvedin acetonitrile/water mixture (3:1, 4 mL) and purified by preparativeLC/MS, SunFire Prep C18 OBD, 5 μm, 19×100 mm, acetonitrile/water 5:95 to100:0+0.1% FA) to afford2-((bis(3-borono-5-chlorophenyl)(oxo)-λ⁶-sulfanylidene)amino)acetic acid(6) as colorless solid.

Yield: 125 mg (29%).

¹H NMR spectrum (300 MHz, Acetone-d₆+D₂O, δ_(H)): 8.39 (bs, 2H); 8.10(bs, 2H); 7.99 (bs, 2H); 3.77 (s, 2H, overlapping with water signal).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 2.70 min.

LC-MS m/z: 432.2 (M+H)⁺.

Example 36 2-((Bis(3-boronophenyl)(oxo)-λ6-sulfanylidene)amino)aceticacid

2-((Bis(3-boronophenyl)(oxo)-λ6-sulfanylidene)amino)acetic acid wassynthesized according to the reaction scheme shown in Chem. 40 andfollowing the procedure described below.

A 25 mL reaction vessel was charged with potassium acetate (1.14 g, 11.6mmol) and the salt was dried for 1 hour at 110 C in vacuo. After coolingto room temperature, the reaction vessel was backfilled with nitrogenand charged with tert-butyl2-((bis(3-chlorophenyl)(oxo)-λ6-sulfanylidene)amino)acetate (1, 925 mg,2.32 mmol), palladium acetate (20.8 mg, 93.0 mol),2-dicyclohexylphosphino-2,4,6-triisopropylbiphenyl (XPhos, 88.2 mg, 0.19mmol) and bis(pinacolato)diboron (1.18 g, 4.64 mmol). The reactionvessel was then evacuated and backfilled with nitrogen (this procedurewas repeated twice), anhydrous tetrahydrofuran (10 mL) was added withsyringe, the vessel was sealed with a plastic stopper and submerged inthe heating bath preheated to 60 C. After stirring at 400 rpm for 16hours the reaction mixture was cooled to ambient temperature, dilutedwith ethyl acetate (40 mL) and filtered through a short plug of silica(25 g) topped with Celite S with the aid of ethyl acetate (3×40 mL). Thefiltrate was concentrated under reduced pressure to afford the crudeproduct 2 as yellowish oil. It was triturated with acetonitrile (10 mL)and the precipitate (XPhos oxide) was filtered. The filtrate wasevaporated in vacuo and co-distilled with cyclohexane (3×20 mL) toafford a yellowish foam, which was pulverized to give tert-butyl2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-λ⁶-sulfanylidene)amino)acetate(2) as yellow oil.

Yield: 1.30 g (96%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.45 (s, 2H); 8.15 (s, 2H);7.94 (d, J=7.3 Hz, 2H); 7.48 (t, J=7.7 Hz, 2H); 3.75 (s, 2H); 1.49 (s,9H); 1.34 (s, 24H).

LC-MS purity: 100% (ELSD, UV 270 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 2.8 min.

LC-MS m/z: 584.6 (M+H)⁺.

Trifluoroacetic acid (12 mL) was added to a solution of tert-butyl2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-λ6-sulfanylidene)amino)acetate(2, 1.30 g, 2.20 mmol) in dichloromethane (4 mL) and the mixture wasstirred for 2 hours at room temperature. The mixture was evaporated todryness in vacuo, and the residue was evaporated from dichloromethane(5×10 mL) to afford of2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-λ⁶-sulfanylidene)amino)aceticacid as off-white foam.

A solution of2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-λ⁶-sulfanylidene)amino)aceticacid (1.00 g, 1.90 mmol) in acetonitrile (12 mL) was diluted with water(4 mL) followed by addition of periodic acid (1.73 g, 7.60 mmol). Theresulting mixture was stirred for 1 hour; and then it was diluted withethyl acetate (100 mL) and washed with 5% brine (3×100 mL). Organicphase was dried over anhydrous sodium sulfate and evaporated to dryness.A part of the residue was dissolved in acetonitrile/water mixture (3:1,4 mL) and purified by preparative LC/MS (SunFire Prep C18 OBD, 5m,19×100 mm, acetonitrile/water 5:95 to 100:0+0.1% FA). The resultingsolution was freeze-dried to afford2-((bis(3-boronophenyl)(oxo)-λ⁶-sulfanylidene)amino)acetic acid (3) aswhite powder.

Yield: 700 mg (80%).

¹H NMR spectrum (300 MHz, Acetone-d₆+D₂O, δ_(H)): 8.50 (s, 2H); 8.05 (t,J=7.8 Hz, 4H); 7.55 (t, J=7.7 Hz, 4H); 3.72 (s, 2H).

LC-MS purity: 100% (ELSD, UV 260 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.19 min.

Example 37N-(1-Hydroxy-5-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-5-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine

N-(1-Hydroxy-5-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-5-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycinewas synthesized according to the reaction scheme shown in Chem. 41 andfollowing the procedure described below.

4-Methyl-2-(trifluoromethyl)benzoic acid (1, 25.0 g, 123 mmol) wasdissolved in sulfuric acid (183 mL) followed by addition ofN-iodosuccinimide (33.1 g, 147 mmol). The resulting mixture was stirredovernight at room temperature then it was poured onto ice.

When ice was completely melted the mixture was extracted with ethylacetate (500 mL). Organic layer was washed with 5% aqueous solution ofsodium thiosulfate (2×250 mL) and water (1×250 mL), dried over anhydroussodium sulfate, filtered and evaporated to dryness affording5-iodo-4-methyl-2-(trifluoromethyl)benzoic acid (2) as beige powder.

Yield: 37.7 g (93%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 13.68 bs, 1H); 8.22 (s, 1H);7.76 (s, 1H); 2.47 (s, 3H).

Mixture of 5-iodo-4-methyl-2-(trifluoromethyl)benzoic acid (2, 22.2 g,67.2 mmol), tri-methyl orthoformate (14.7 mL, 134 mmol) andmethanesulfonic acid (2.8 mL) in methanol (135 mL) was refluxed at 80°C. under nitrogen atmosphere overnight. Solvent was evaporated. Theresidue was dissolved in 5% aqueous solution of sodium carbonate (200mL) and extracted with ethyl acetate (3×250 mL). Combined organic layerswere washed with water (1×300 mL) and brine (1×200 mL), dried overanhydrous sodium sulfate, filtered and evaporated. The residue waspurified by quick flash column chromatography (Silicagel 60, 0.040-0.063mm; eluent: cyclohexane/ethyl acetate 9:1) to give methyl5-iodo-4-methyl-2-(trifluoromethyl)benzoate (3) as white crystals.Yield: 35.9 g (91%).

R_(F) (cyclohexane/ethyl acetate 9:1): 0.50.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.26 (s, 1H); 7.57 (s, 1H);3.93 (s, 3H); 2.53 (s, 3H).

A mixture of methyl 5-iodo-4-methyl-2-(trifluoromethyl)benzoate (3, 35.9g, 104 mmol), N-bromosuccinimide (20.4 g, 114 mmol) and2,2-azobis(2-methylpropionitrile) (AIBN, 5.12 g, 31.2 mmol) inbenzotrifluoride (95 mL) was stirred at 85° C. overnight. Fullconversion was not achieved but the reaction was worked up.Dichloromethane (150 mL) was added and the mixture was washed with water(3×100 mL). Organic layer was dried over anhydrous sodium sulfate,filtered and evaporated. The residue was dissolved in acetonitrile (440mL) and potassium acetate (10.2 g, 104 mmol) was added. The mixture wasstirred at 75 C overnight. The insoluble material was filtered off andthe filtrate was evaporated. The residue was purified by flash columnchromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/dichloromethane 4:1 to 1:1.5) to give methyl4-(acetoxymethyl)-5-iodo-2-(trifluoromethyl)benzoate (4) as whitepowder. Yield: 17.5 g (42%).

R_(F) (cyclohexane/ethyl acetate 9:1): 0.35.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.28 (s, 1H); 7.70 (s, 1H);5.16 (s, 2H); 3.95 (s, 3H); 2.20 (s, 3H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −59.96 (s).

A mixture of methyl 4-(acetoxymethyl)-5-iodo-2-(trifluoromethyl)benzoate(4, 17.5 g, 43.5 mmol), bis(pinacolato)diboron (14.3 g, 56.5 mmol) anddry potassium acetate (21.3 g, 217 mmol) in dry N,N-dimethylsulfoxide(110 mL) was degassed; then[1,1-bis(diphenylphosphino)ferrocene]dichloropalladium (1.59 g, 2.17mmol) was added. Reaction mixture was stirred under nitrogen atmosphereat 95° C. overnight. After cooling down diethyl ether (500 mL) was addedand the precipitate was filtered off through celite pad. The filtratewas washed with 5% aqueous solution of sodium chloride (3×500 mL).Organic layer was dried over anhydrous sodium sulfate, filtered andevaporated affording methyl4-(acetoxymethyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-(trifluoromethyl)benzoate(5) as black oil. This oil was used in the next step without furtherpurification. Yield: 22.5 g.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.22 (s, 1H); 7.74 (s, 1H);5.44 (s, 2H); 3.94 (s, 3H); 2.14 (s, 3H); 1.36 (s, 12H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, 6:-60.07 (s).

Methyl4-(acetoxymethyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-(trifluoromethyl)benzoate(5, 17.5 g, 43.5 mmol) was suspended in a solution of sodium hydroxide(8.70 g, 217 mmol) in water (150 mL). The mixture was stirred for 6hours at room temperature then it was extracted with diethyl ether(2×200 mL). Aqueous phase was acidified with concentrated hydrochloricacid (18.9 mL) and resulting mixture was stirred overnight at roomtemperature. The precipitate was filtered, washed with water and driedto give1-hydroxy-5-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (6) as grey powder.

Yield: 7.62 g (71%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 13.50 (bs, 1H); 9.57 (s, 1H);8.16 (s, 1H); 7.92 (s, 1H); 5.11 (s, 2H).

¹⁹F NMR spectrum (282 MHz, DMSO-d₆, δ_(F)): −57.91 (s).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 2.77 min.

LC-MS m/z: 245.9 (M−H)⁻.

1-Hydroxy-5-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (6, 6.71 g, 27.3 mmol) was dissolved intetrahydrofuran/dichloromethane mixture (1:1, 50 mL) followed byaddition of 2,3,4,5,6-pentrafluorophenol (5.03 g, 27.3 mmol) andN-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (5.23 g,27.3 mmol). The mixture was stirred overnight at room temperature.Solvent was evaporated. The residue was dissolved in ethyl acetate (150mL) and washed with water (3×100 mL) and brine (1×100 mL). Organic layerwas dried over anhydrous sodium sulfate, filtered and evaporated. Theresidue was dissolved in diethyl ether (10 mL) and n-hexane (200 mL) wasadded. The precipitate was filtered off and the filtrate was evaporated.The same procedure was repeated with the precipitate twice. All thefiltrates were combined together and evaporated to dryness to affordperfluorophenyl1-hydroxy-5-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(7) as yellow tough oil.

Yield: 9.76 g (87%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.74 (s, 1H); 8.53 (s, 1H);8.16 (s, 1H); 5.18 (s, 2H).

Perfluorophenyl1-hydroxy-5-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(7, 9.51 g, 23.1 mmol) was dissolved in N,N-dimethylformamide (30 mL).Subsequently N,N-diisopropylethylamine (10.1 mL, 57.7 mmol) and asolution of (2-aminoethyl)glycine hydrochloride (8, 1.78 g, 11.5 mmol)in water (30 mL) were added. Resulting mixture was stirred overnight atroom temperature. Then the solvents were evaporated. The residue wasdissolved in ethyl acetate (200 mL) and washed 1 M aqueous solution ofhydrochloric acid (1×200 mL), water (2×200 mL) and brine (1×150 mL).Organic layer was dried over anhydrous sodium sulfate, filtered andevaporated.

The residue was treated with cyclohexane. The precipitate was filtered,washed with cyclohexane and purified by flash column chromatography(Silicagel 60, 0.040-0.063 mm; eluent: dichloromethane/methanol/formicacid 10:1:0.05). Fractions containing product were combined andevaporated. The residue was treated with cyclohexane. The precipitatewas filtered, washed with cyclohexane, dissolved in acetonitrile (50 mL)and freeze-dried to give the title compound (9) as beige powder. Yield:3.63 g (55%).

¹H NMR spectrum (300 MHz, AcOD-d₄, 80 C, δ_(H)): 8.04-7.66, 4H);5.28-5.04 (m, 4H); 4.63-4.34 (m, 1H); 4.22-3.78 (m, 3H); 3.72-3.49 (m,2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 4.15 min.

LC-MS m/z: 574.0 (M+H)⁺.

Example 382-((Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborol-6-yl)(oxo)-λ6-sulfanylidene)amino)aceticacid

2-((Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborol-6-yl)(oxo)-λ6-sulfanylidene)amino)aceticacid was synthesized according to the reaction scheme shown in Chem. 42and Chem. 43 and following the procedure described below.

Solution of 3-bromo-4-methyl-5-trifluoromethylbenzoicacid (1, 26.6 g,94.0 mmol), triethylamine (16.0 mL, 113 mmol) and diphenyl phosphorylazide (24.0 mL, 113 mmol) in mixture of N,N-dimethylformamide andtert-butanol (1:5, 0.5 L) was stirred at 110° C. for 5 hours. Thereaction mixture was then evaporated and crude product was dissolved inethyl acetate (0.5 L) and washed with 10 aqueous solution of citric acid(300 mL), 10% aqueous solution of sodium bicarbonate (300 mL) and brine(300 mL). Organic layer was separated, dried over anhydrous sodiumsulfate, filtered and evaporated. Crude product was purified by columnchromatography (Silicagel, 0.063-0.200 mm; eluent: cyclohexane/ethylacetate 9:1) to provide tert-butyl(3-bromo-4-methyl-5-(trifluoromethyl)phenyl)carbamate (2) as white solid.

Yield: 13.5 g (41%/).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 7.91 (s, 1H); 7.55 (d, J1=2.4Hz, 1H); 6.49 (bs, 1H); 2.47 (d, J1=1.5 Hz, 3H); 1.54 (s, 9H).

tert-Butyl(3-bromo-4-methyl-5-(trifluoromethyl))phenyl)carbamate (2,10.0 g, 28.2 mmol) was dissolved in 2-propanol (60 mL) and concentratedaqueous hydrochloric acid (15 mL) was added. After 48 hours, thereaction mixture was evaporated, taken up in diethylether (100 mL) waswashed with 1 M aqueous solution of sodium hydroxide (100 mL) and brine(100 mL). Organic layer was dried over anhydrous sodium sulfate,filtered and evaporated to give the crude3-bromo-4-methyl-5-(trifluoromethyl)aniline (3) as yellowish oil, whichwas taken to the next step without purification.

3-Bromo-4-methyl-5-(trifluoromethyl)aniline (3) was dissolved inice-cold acetonitrile (110 mL) and 4-toluenesulfonic acid monohydrate(16.1 g, 84.6 mmol) was added. Ice-cold water (45 mL) was added to themixture to improve stirring. A solution of sodium nitrite (3.90 g, 56.4mmol) and potassium iodide (11.7 g, 70.5 mmol) in water (30 mL) was thenadded dropwise to the acetonitrile solution (cooled in an ice-bath).After the addition had been completed and the gas evolution had ceased,the reaction mixture was allowed to reach ambient temperature andstirred for 2 hours. The reaction mixture was concentrated under reducedpressure and taken up in diethyl ether (100 mL) and washed with 10%aqueous solution of potassium carbonate (100 mL) and 10% aqueoussolution of sodium thiosulfate (50 mL). Organic layer was dried overanhydrous sodium sulfate, filtered and evaporated to give the crudeproduct, which was subjected to flash column chromatography (Silicagel60, 0.063-0.200 mm; eluent: neat cyclohexane) to give1-bromo-5-iodo-2-methyl-3-(trifluoromethyl)benzene (4) as yellow oil.Yield: 7.06 g (69%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.09 (s, 1H); 7.89 (s, 1H);2.49 (s, 3H).

A mixture of 1-bromo-5-iodo-2-methyl-3-(trifluoromethyl)benzene (4, 6.65g, 18.2 mmol), N-bromosuccinimide (4.22 g, 23.7 mmol) and AIBN (299 mg,1.82 mmol) was suspended in benzotrifluoride (27 mL) and heated to 85°C. (oil bath) for 24 hours. More AIBN (299 mg, 1.82 mmol) was added andthe reaction mixture was heated with stirring for additional 24 hours.After cooling to ambient temperature, the reaction mixture was taken indiethyl ether (100 mL) and washed with 10% aqueous solution of potassiumbicarbonate (100 mL), water (100 mL), 10% aqueous solution of sodiumthiosulfate (50 mL), water (50 mL) and brine (50 mL). Organic layer wasdried over anhydrous sodium sulfate, filtered and evaporated to give thecrude benzylic bromide. It was dissolved in dry acetonitrile (27 mL) andpotassium acetate (3.60 g, 36.0 mmol) was added. The resultingsuspension was heated to 80° C. (oil bath) for 24 hours. After coolingto ambient temperature, the reaction mixture was taken in diethyl ether(100 mL) and filtered through a short plug of Silica gel (50 g) toppedwith Celite. Filtrate was evaporated in vacuo and the residue wassubjected to flash column chromatography (Silicagel 60, 0.063-0.200 mm;eluent: cyclohexane/ethyl acetate 10:1) to give2-bromo-4-iodo-6-(trifluoromethyl)benzyl acetate (5) as colorless solid.

Yield: 6.60 g (85%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.20 (s, 1H); 8.00 (s, 1H);5.27 (s, 2H); 2.09 (s, 3H).

2-Bromo-4-iodo-6-(trifluoromethyl)benzyl acetate (5, 5.16 g, 12.2 mmol)was dissolved in dry methanol (36 mL) and potassium carbonate (5.00 g,36.2 mmol) was added. After 90 minutes, the reaction mixture was takenin diethyl ether (100 mL) and filtered through a short plug of Silicagel (50 g) topped with Celite. The filtrate was evaporated in vacuo togive pure 2-bromo-4-iodo-6-(trifluoromethyl)phenyl)methanol (6) ascolorless solid.

Yield: 4.64 g (quant.).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.18 (s, 1H); 7.98 (s, 1H);4.87 (d, J=6.9 Hz, 2H), 2.08 (t, J=6.9 Hz, 1H).

2-Bromo-4-iodo-6-(trifluoromethyl)phenyl)methanol (6, 4.64 g, 12.2 mmol)was dissolved in dry ice-cold dichloromethane (36 mL) andN,N-diisopropylethylamine (DIPEA, 4.20 mL, 24.4 mmol) was added,followed by ethoxymethyl chloride (1.45 mL, 15.6 mmol). The reactionmixture was allowed to reach ambient temperature and stirred for 48hours before it was quenched with methanol (5 mL). After 2 hours, thereaction mixture was evaporated in vacuo and the residue was taken up indiethyl ether (100 mL) and washed with 10% aqueous solution of potassiumbisulfate (100 mL), water (100 mL) and brine (50 mL). Organic layer wasdried over anhydrous sodium sulfate, filtered and evaporated. Theresidue was subjected to flash column chromatography (Silicagel 60,0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 20:1) to give1-bromo-2-((ethoxymethoxy)methyl)-5-iodo-3-(trifluoromethyl)benzene (7)as colorless solid.

Yield: 4.57 g (85%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.20 (s, 1H); 7.98 (s, 1H);4.83 (s, 2H); 4.75 (s, 2H); 3.71 (q, J=7.1 Hz, 2H); 1.27 (t, J=7.1 Hz,3H).

1-Bromo-2-((ethoxymethoxy)methyl)-5-iodo-3-(trifluoromethyl)benzene (7,3.32 g, 7.57 mmol) was dissolved in dry tetrahydrofuran (23 mL) underinert atmosphere and cooled to 30 C (methanol/dry ice bath). 1.3 MSolution isopropylmagnesium chloride-lithium chloride complex intetrahydrofuran (6.10 mL, 7.93 mmol) was added dropwise with stirring.After 30 minutes, a solution of bis(phenylsulfonyl)sulfide (1.07 mg,3.41 mmol) in dry tetrahydrofuran (10 mL) was added dropwise. Thereaction mixture was then allowed to reach slowly ambient temperature(cooling bath was allowed to expire) and then quenched with 10% aqueoussolution of ammonium chloride (15 mL). The reaction mixture was taken upin diethyl ether (50 mL) and washed with water (50 mL) and brine (50mL). Organic layer was dried over anhydrous sodium sulfate, filtered andevaporated. The residue was subjected to flash column chromatography(Silicagel 60, 0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 30:1)to givebis(3-bromo-4-((ethoxymethoxy)methyl)-5-(trifluoromethyl)phenyl)sulfane(8) as colorless solid. Yield: 1.96 g (87%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.76 s, 2H); 7.65 (s, 2H); 4.84(s, 4H); 4.79 (s, 4H); 3.71 (q, J=7.1 Hz, 4H); 1.26 (t, J=7.1 Hz, 6H).

To a well-stirred solution ofbis(3-bromo-4-((ethoxymethoxy)methyl)-5-(trifluoromethyl)phenyl)sulfane(1, 997 mg, 1.52 mmol, compound)) in mixture of tetrahydrofuran (3 mL)and methanol (6 mL) was added ammonium carbamate (238 mg, 3.04 mmol) andbis(acetoxy)iodobenzene (1.22 g, 3.80 mmol). After 3 hours, to thereaction mixture more ammonium carbamate (119 mg, 1.52 mmol) andbis(acetoxy)iodobenzene (611 mg, 1.90 mmol) were added. After six morehours, to the reaction mixture more ammonium carbamate (119 mg, 1.52mmol) and bis(acetoxy)iodobenzene (611 mg, 1.90 mmol) were added andstirred for 10 more hours. The reaction mixture was then evaporated andcrude product was dissolved in ethyl acetate (40 mL) and washed with 10%aqueous solution of sodium thiosulfate (40 mL), 10% aqueous solution ofpotassium bicarbonate (40 mL) and brine (40 mL). Organic layer wasseparated, dried over anhydrous sodium sulfate, filtered and evaporated.The crude product was recrystallized from hexane to givebis(3-bromo-4-((ethoxymethoxy)methyl)-5-(trifluoromethyl)phenyl)(imino)-λ⁶-sulfanone2. Yield: 800 mg (77%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.45 (s, 2H); 8.27 (s, 2H);4.81 (app. s, 8H); 3.67 (q, J=7.0 Hz, 4H); 3.33 (bs, 1H); 1.23 (t, J=7.0Hz, 6H). LC-MS purity: 100% (ELSD, UV 242).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 85:15 to100:0+0.1% FA): 1.56 min.

LC-MS m/z: 688.3 (M+H)⁺.

To an ice-cold, well-stirred solution ofbis(3-bromo-4-((ethoxymethoxy)methyl)-5-(trifluoromethyl)phenyl)(imino)-λ⁶-sulfanone(2, 756 mg, 1.10 mmol) in anhydrous N,N-dimethylformamide was addedsodium hydride (58.0 mg, 1.43 mmol) under nitrogen. After 5 minutes,tert-butyl bromoacetate (321 mg, 1.65 mmol) was added. The reactionmixture was allowed to reach ambient temperature and stirred for anhour. The reaction mixture was then taken up in ethyl acetate (40 mL)and washed with 10% aqueous solution of ammonium chloride (40 mL), water(2×40 mL) and brine (40 mL). Organic layer was separated, dried overanhydrous sodium sulfate, filtered and evaporated. The crude product waspurified by column chromatography (Silicagel, 0.063-0.200 mm; eluent:cyclohexane/ethyl acetate 10:1) to provide tert-butyl2-((bis(3-bromo-4-((ethoxymethoxy)methyl)-5-(trifluoromethyl)phenyl)(oxo)-λ⁶-sulfanylidene)amino)-acetate(3) as colorless oil. Yield: 847 mg (96%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.47 (s, 2H); 8.28 (s, 2H);4.81 (app. s, 8H); 3.77 (s, 2H); 3.67 (q, J=7.0 Hz, 4H); 1.49 (s, 9H);1.23 (t, J=7.0 Hz, 6H).

LC-MS purity: 100% (ELSD, UV 242).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 85:15 to100:0+0.1% FA): 3.04 min.

LC-MS m/z: 802.5 (M+H)⁺.

A 50 mL reaction vessel was charged with potassium acetate (490 mg, 5.00mmol) and the salt was dried for 1 hour at 110° C. in vacuo. Aftercooling to room temperature, the reaction vessel was backfilled withnitrogen and charged with tert-butyl2-((bis(3-bromo-4-((ethoxymethoxy)methyl)-5-(trifluoromethyl)phenyl)(oxo)-λ⁶-sulfanylidene)amino)-acetate(3, 801 mg, 1.00 mmol),(1,1-bis(diphenylphosphino)ferrocene)-dichloropalladium(II), complexwith dichloromethane (41.0 mg, 50.0 mol) and bis(pinacolato)diboron (635mg, 2.50 mmol). The reaction vessel was then evacuated and backfilledwith nitrogen (this procedure was repeated twice), anhydrous 1,4-dioxane(5 mL) was added with syringe, the vessel was sealed with a plasticstopper and submerged in the heating bath preheated to 80° C. Afterstirring at 400 rpm for 16 hours (overnight) the reaction mixture wascooled to ambient temperature, diluted with ethyl acetate (30 mL) andfiltered through a short plug of silica (10 g) topped with Celite S withthe aid of ethyl acetate (3×30 mL). The filtrate was concentrated underreduced pressure to afford the tert-butyl2-((bis(4-((ethoxymethoxy)methyl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)(oxo)-λ⁶-sulfanylidene)-amino)acetate(4) as brownish waxy foam. It was dissolved in acetonitrile (6 mL) andwater (1 mL) and periodic acid (912 mg, 4.00 mmol) was added. After twohours, the reaction mixture was taken up was taken up in ethyl acetate(30 mL) and washed with water (2×30 mL) and brine (40 mL). Organic layerwas dried over anhydrous sodium sulfate, filtered and evaporated to givethe crude product as orange wax. It was dissolved in tetrahydrofuran (4mL) and water (1 mL) and concentrated solution of hydrochloric acid (1mL) was added. After two hours, the reaction mixture was taken heated to50 C and stirred for 5 hours. Afterwards, it was taken up in ethylacetate (30 mL) and washed with water (30 mL) and brine (40 mL). Organiclayer was dried over anhydrous sodium sulfate, filtered and evaporatedto give the crude product as beige solid. It was dissolved in a minimumamount of diethyl ether and hexane (3 volumes) was added. Theprecipitated product was collected by filtration, washed with coldhexane (2×5 mL) and air dried to give2-((bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo-[c][1,2]oxaborol-6-yl)(oxo)-λ6-sulfanylidene)amino)aceticacid (5) as off-white solid. Yield: 405 mg (78%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂O, δ_(H)): 8.68 (s, 2H); 8.47 (s,2H); 5.21 (s, 4H); 3.83 (s, 2H) partly overlapping with water signal.

LC-MS purity: 100% (ELSD)

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 3.84 min.

LC-MS m/z: 524.3 (M+H)⁺

Example 39 (3-Borono-5-((3-boronophenyl)sulfonyl)benzoyl)glycine

(3-Borono-5-((3-boronophenyl)sulfonyl)benzoyl)glycine was synthesizedaccording to the reaction scheme shown in Chem. 44 and following theprocedure described below.

3-Bromo-5-iodobenzoic acid (1, 32.7 g, 100 mmol) was suspended inmethanol (150 mL) and methanesulfonic acid (3 mL) was added. Theresulting mixture was stirred for hours at 60° C. (oil bath). Theresulting clear solution was cooled to −20° C. in the freezer for 20hours and the resulting solid was collected by filtration, washed withchilled (−20 C) methanol and dried in vacuo to give methyl3-bromo-5-iodobenzoate (2) as an off-white solid.

Yield: 26.0 g (76%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.30 (s, 1H); 8.14 (s, 1H);8.04 (s, 1H); 3.93 (s, 1H).

Methyl 3-bromo-5-iodobenzoate (2, 2.62 g, 10.0 mmol), anhydrouspotassium carbonate (3.45 g, 25.0 mmol), copper iodide (381 mg, 2.00mmol) and 3-bromobenzenethiol (3, 1.78 mL, 15.0 mmol) were suspended indry 1,2-dimethoxyethane (25 mL) and the resulting suspension was stirredfor 48 hours at 80° C. After cooling to ambient temperature, thereaction mixture was diluted with cyclohexane (80 mL), filtered througha pad of silicagel (40 g) topped with Celite (washed with ethylacetate/cyclohexane 1:10, 3×30 mL) and evaporated in vacuo. The residuewas dissolved in acetic acid (30 mL) and 30% aqueous solution ofhydrogen peroxide (4.00 mL, 39.2 mmol) was added in portions (heatevolution). After stirring for 16 hours at 80° C. (oil bath), thereaction mixture was evaporated in vacuo, taken up in ethyl acetate (100mL) and washed with water (100 mL) and brine (100 mL). Drying of theorganic layer with anhydrous sodium sulfate, filtration and evaporationin vacuo gave the methyl ester 5 as yellow oil. It was dissolved intetrahydrofuran (30 mL) and water (15 mL) and lithium hydroxidemonohydrate (840 mg, 20.0 mmol) was added. After stirring for 48 hours,the reaction mixture was evaporated in vacuo, taken up in ethyl acetate(100 mL) and washed with 1 M aqueous solution of hydrochloric acid (100mL) and brine (100 mL). Drying of the organic layer with anhydroussodium sulfate, filtration and evaporation in vacuo gave the crudeproduct as brownish solid. It was purified by recrystallization fromtoluene to give pure 3-bromo-5-((3-bromophenyl)sulfonyl)benzoic acid (6)as beige solid. Yield: 1.67 g (40%).

¹H NMR spectrum (300 MHz, Acetone-d₆, δ_(H)): 8.53 (s, 1H); 8.45 (s,1H); 8.38 (s, 1H); 8.27 (s, 1H); 8.12 (d, J=8.0 Hz, 1H); 7.92 (d, J=7.9Hz, 1H); 7.64 (t, J=8.0 Hz, 1H).

LC-MS purity: 100% (ELSD, UV 242 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 3.63 min.

LC-MS m/z: 421.2 (M+H)⁺.

A solution of 3-bromo-5-((3-bromophenyl)sulfonyl)benzoic acid (6, 924mg, 2.20 mmol) and carbonyldiimidazole (CDI, 428 mg, 2.64 mmol) inanhydrous acetonitrile (8.0 mL) was stirred for 16 hours. Glycinetert-butyl ester hydrochloride (480 mg, 2.86 mmol) was then added,followed by triethylamine (1 mL). After stirring for 16 hours, thereaction mixture was evaporated in vacuo, taken up in ethyl acetate (30mL) and washed with 1 M aqueous solution of potassium bisulfate (100 mL)and brine (100 mL). Drying of the organic layer with anhydrous sodiumsulfate, filtration and evaporation in vacuo gave the crude product asyellowish solid, which was subjected to flash column chromatography(Silicagel 60, 0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 5:1 to4:1) to give tert-butyl(3-bromo-5-((3-bromophenyl)sulfonyl)benzoyl)glycinate (7) as white foam.

Yield: 1.08 g (92%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.26 (s, 1H); 8.18 (s, 1H);8.15 (s, 1H); 8.09 (s, 1H); 7.89 (d, J=7.9 Hz, 1H); 7.79-7.69 (m, 1H);7.43 (t, J=7.9 Hz, 1H); 6.76 (bs, 1H); 4.13 (d, J=5.0 Hz, 2H); 1.51 (s,9H).

LC-MS purity: 100% (ELSD, UV 242 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 4.13 min.

LC-MS m/z: 534.3 (M+H)⁺.

A 25 mL reaction vessel was charged with potassium acetate (490 mg, 5.00mmol) and the salt was dried for 1 hour at 110° C. in vacuo. Aftercooling to room temperature, the reaction vessel was backfilled withnitrogen and charged with methyl tert-butyl(3-bromo-5-((3-bromophenyl)sulfonyl)benzoyl)glycinate (7, 533 mg, 1.00mmol), palladium acetate (8.90 mg, 0.04 mmol),2-dicyclohexylphosphino-2,4,6-triisopropylbiphenyl (XPhos, 39.0 mg, 0.08mmol) and bis(pinacolato)diboron (610 mg, 2.40 mmol). The reactionvessel was then evacuated and backfilled with nitrogen (this procedurewas repeated twice), anhydrous tetrahydrofuran (5 mL) was added withsyringe, the vessel was sealed with rubber septum and submerged in theheating bath preheated to 60° C. After stirring at 400 rpm for 16 hours(overnight) the reaction mixture was cooled to ambient temperature,diluted with cyclohexane (24 mL) and filtered through a short plug ofsilica (7 g) topped with Celite S with the aid of dichloromethane (3×15mL). The filtrate was concentrated under reduced pressure to afford theintermediate tert-butyl(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-((3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)sulfonyl)benzoyl)glycinate(8) as brownish waxy solid. It was dissolved in a mixture of1,2-dichloroethane (2.5 mL) and trifluoroacetic acid (2.5 mL). After twohours, the reaction mixture was evaporated in vacuo and the residue wasco-distilled with ethyl acetate (3×10 mL). The resulting foam wasdissolved in acetonitrile (6 mL) and water (2 mL) and periodic acid(1.37 g, 6.00 mmol) was added. The resulting mixture was vigorouslystirred at ambient temperature for two hours. The reaction mixture wastaken up in ethyl acetate (30 mL) and washed with water (2×20 mL) andbrine (20 mL. The organic layer was extracted with 1 M aqueous solutionof sodium hydroxide (20 mL) and water (10 mL), the aqueous extracts werecombined and washed with dichloromethane (2×10 mL). The aqueous phasewas acidified by the addition of concentrated hydrochloric acid (3 mL)and extracted with ethyl acetate (2×20 mL). The combined organicextracts were washed with brine (15 mL), dried over anhydrous sodiumsulfate, filtered and evaporated. The crude product was dissolved in aminimum amount of wet (shaken thoroughly with water) ethyl acetate andthe solution added dropwise to an ice-cold n-hexane (5 mL) withstirring, resulting in the precipitation of a product. The solid wascollected by filtration and washed with hexane (2×5 mL) to give thetitle (3-borono-5-((3-boronophenyl)sulfonyl)benzoyl)glycine (9) ascolorless solid.

Yield: 221.0 mg (54%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂0; 10:1, δ_(H)): 8.64-8.50 (m,3H); 8.46 (s, 1H); 8.15-7.99 (m, 2H); 7.59 (t, J=7.7 Hz, 1H); 4.22-4.04(m, 2H).

LC-MS purity: 100% (ELSD, UV 242 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 2.45 min.

LC-MS m/z: 408.4 (M+H)⁺.

Example 40(S)-2,3-Bis(1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid

(S)-2,3-Bis(1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid was synthesized according to the reaction scheme shown in Chem. 45and following the procedure described below.

Concentrated sulfuric acid (96%, 1.00 mL, 18.0 mmol) was added to asolution of 3-bromo-4-methylbenzoic acid (1, 25.0 g, 116 mmol) inmethanol (500 mL) and the reaction mixture was allowed to stir at 60° C.for 43 hours. The solution was cooled to room temperature, sodiumhydrogencarbonate (4.39 g, 53.3 mmol) was added, and the mixture wasevaporated under reduced pressure. The residue was partitioned betweenethyl acetate (600 mL) and water (250 mL). The organic layer wasseparated; washed with 0.5 M aqueous solution of sodium hydroxide (2×250mL), 5% aqueous solution of sodium carbonate (2×200 mL), 0.5 M aqueoussolution of hydrochloric acid (200 mL), water (200 mL) and brine (150mL); dried over anhydrous sodium sulfate and evaporated in vacuo to givemethyl 3-bromo-4-methylbenzoate (2) as orange oil. Yield: 25.16 g (94%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 9:1): 0.45.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.21 (d, J=1.7 Hz, 1H); 7.87(dd, J=7.9 and 1.7 Hz, 1H); 7.30 (d, J=7.9 Hz, 1H); 3.92 (s, 3H); 2.46(s, 3H).

A stirred mixture of 3-bromo-4-methylbenzoate (2, 24.8 g, 108 mmol),1-bromo-pyrrolidine-2,5-dione (NBS, 21.2 g, 119 mmol) and water (360 mL)in a wide beaker was placed under D3 basking lamp for reptiles (100 W,UVA, UVB, IR) and heated to 70-80° C. Another portion of1-bromopyrrolidine-2,5-dione (NBS, 3.86 g, 21.7 mmol) was added after 4hours, and the mixture was stirred for an additional one hour. Themixture was cooled to room temperature followed by extraction with ethylacetate (2×250 mL). Combined organic layers were washed with water(4×200 mL), dried over anhydrous sodium sulfate and evaporated in vacuoto afford crude methyl 3-bromo-4-(bromomethyl)benzoate (3) as yellowoil. Yield: 34.06 g (74%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 9:1): 0.30.

¹H NMR purity: 72 wt %.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.25 (d, J=1.7 Hz, 1H); 7.96(dd, J=8.1 and 1.7 Hz, 1H); 7.54 (d, J=8.1 Hz, 1H); 4.61 (s, 2H); 3.94(s, 3H).

A mixture of the above crude methyl 3-bromo-4-(bromomethyl)benzoate (3,72%, 34.1 g, 80.1 mmol) and potassium acetate (23.6 g, 240 mmol) inacetonitrile (800 mL) was heated at 75° C. for 5 hours. The mixture wascooled to room temperature, the solid was removed by filtration andwashed with ethyl acetate (3×50 mL). The filtrate was evaporated todryness, and the residue was partitioned between ethyl acetate (700 mL)and water (200 mL). The organic layer was separated, washed with water(200 mL) and brine (2×200 mL), dried over anhydrous sodium sulfate andevaporated in vacuo. The residue was purified by flash columnchromatography (Silicagel, 0.063-0.200 mm; eluent: cyclohexane/ethylacetate 97:3) to give pure methyl 4-(acetoxymethyl)-3-bromobenzoate (4)as white solid. Yield: 19.39 g (84%).

R_(F) (SiO₂, n-hexane/ethyl acetate 4:1): 0.25.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.24 (d, J=1.5 Hz, 1H); 7.99(dd, J=8.0 and 1.6 Hz, 1H); 7.48 (d, J=8.1 Hz, 1H); 5.23 (s, 2H); 3.94(s, 3H); 2.18 (s, 3H).

LC-MS purity: 100% (UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 50:50 to100:0+0.1% FA): 2.41 min.

LC-MS m/z: 287.2; 289.2 (M+H)⁺.

[1,1-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (2.32 g, 3.18mmol) was added to a degassed solution of methyl4-(acetoxymethyl)-3-bromobenzoate (4, 18.2 g, 63.5 mmol),bis(pinacolato)diboron (17.7 g, 69.9 mmol) and potassium acetate (18.7g, 191 mmol) in dry 1,4-dioxane (165 mL) under argon. The mixture waswarmed to 80° C. and stirred at this temperature for 16 hours. Themixture was cooled to room temperature; then it was diluted withdichloromethane (165 mL) and passed through a short column of silicageltopped with Celite followed by elution with dichloromethane. Fractionscontaining the product were combined and evaporated to dryness. Theresidue was purified by flash column chromatography (Silicagel,0.063-0.200 mm; eluent: cyclohexane/ethyl acetate 9:1 to 7:3) to yieldmethyl4-(acetoxymethyl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(5) as yellow solid. Yield: 21.80 g (>100%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 9:1): 0.15.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.49 (d, J=1.8 Hz, 1H); 8.10(dd, J=8.1 and 2.0 Hz, 1H); 7.46 (d, J=8.1 Hz, 1H); 5.43 (s, 2H); 3.93(s, 3H); 2.12 (s, 3H), 1.36 (s, 12H).

LC-MS purity: 100% (ELSD), 88% (UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 50:50 to100:0+0.1% FA): 3.26 min.

LC-MS m/z: 335.5 (M+H)⁺.

Methyl4-(acetoxymethyl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(5, 21.8 g, <63.5 mmol) was added to a solution of sodium hydroxide(12.7 g, 318 mmol) in water (200 mL) and the resulting mixture wasstirred at room temperature for 5 hours. The mixture was filtered,washed with diethyl ether (200 mL) and acidified with 35% hydrochloricacid (39.6 mL, 444 mmol). The resulting white suspension was placed inthe fridge over weekend. The precipitate was filtered, washed with water(3×50 mL) and suspended in 20% aqueous solution of acetonitrile (100mL). The mixture was freeze-dried to afford1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylic acid (6) aswhite powder. Yield: 10.63 g (94%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.90 (s, 1H); 9.35 (s, 1H);8.37 (s, 1H); 8.04 (dd, J=8.0 and 1.6 Hz, 1H); 7.52 (d, J=7.9 Hz, 1H);5.05 (s, 2H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.90 min.

LC-MS m/z: 179.2 (M+H)⁺.

N,N′-Dicyclohexylcarbodiimide (DCC, 2.50 g, 12.1 mmol) was added to asuspension of 1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (6, 2.16 g, 12.1 mmol) and pentafluorophenol (PfpOH, 2.23 g, 12.1mmol) in acetonitrile (150 mL) and the mixture was stirred at roomtemperature overnight. The solid was filtered off and washed with ethylacetate (5×20 mL). The filtrates were combined and evaporated todryness. Cyclohexane (100 mL) was added to the residue and the mixturewas stirred at room temperature for 15 minutes. The mixture was decantedand the sediment was dried in vacuo to give perfluorophenyl1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (7) asoff-white solid. Yield: 2.67 g (64%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.62 (s, 1H); 8.32 (dd, J=8.1and 1.7 Hz, 1H); 7.55 (d, J=8.3 Hz, 1H); 5.22 (s, 2H).

LC-MS purity: 98% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 4.08 min.

LC-MS m/z: 345.3 (M+H)⁺.

Triethylamine (1.65 mL, 11.8 mmol) was added to a mixture ofperfluorophenyl1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate (7, 713 mg,2.07 mmol) and L-2,3-diaminopropionic acid hydrochloride (8,L-Dap-OHHCl, 139 mg, 0.99 mmol) in N,N-dimethylformamide (10.0 mL) andthe resulting solution was stirred at room temperature over weekend. Themixture was evaporated to dryness in vacuo, and the residue waspartitioned between 1 M aqueous solution of hydrochloric acid (25 mL)and ethyl acetate (50 mL). The phases were separated and the organic onewas extracted with ethyl acetate (2×25 mL). All organic layers wascombined, dried over anhydrous sodium sulfate and concentrated in vacuoto approx. 3 mL volume. Cyclohexane (100 mL) was added and the resultingsuspension was stirred at room temperature overnight. The precipitatewas collected by filtration and dried in vacuo. The precipitate (crude9, 288 mg) was dissolved in 50% aqueous solution of acetonitrile (4.8mL) and subjected to purification by preparative LC/MS (SunFire Prep C18OBD, 5m, 19×100 mm, acetonitrile/water 5:95 to 100:0+0.1% FA). Purefractions were combined and freeze-dried to give title compound (9) aswhite powder. Yield: 116 mg (28%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 12.73 (bs, 1H); 9.33 (s, 1H);9.30 (s, 1H); 8.76 (d, J=7.5 Hz, 1H); 8.70 (t, J=5.9 Hz, 1H); 8.25 (d,J=0.7 Hz, 1H); 8.20 (d, J=0.9 Hz, 1H); 7.96 (dd, J=8.1 and 1.7 Hz, 1H);7.90 (dd, J=7.9 and 1.7 Hz, 1H); 7.52 (d, J=8.8 Hz, 1H); 7.48 (d, J=8.3Hz, 1H); 5.05 (s, 2H); 5.03 (s, 2H); 4.71-4.62 (m, 1H); 3.81-3.73 (m,2H).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.56 min.

LC-MS m/z: 425.4 (M+H)⁺.

Example 41N-(1-Hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-ethyl)glycine

N-(1-Hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-ethyl)glycinewas synthesized according to the reaction scheme shown in Chem. 46 andfollowing the procedure described below.

Mixture of methyl 3-(benzoylthio)-5-bromo-4-methylbenzoate (1, 2.90 g,7.95 mmol) and potassium carbonate (2.19 g, 15.9 mmol) was dissolvedwhile heated in dry methanol (100 mL) and then was stirred undernitrogen atmosphere at room temperature for 2 hours. The solvent wasevaporated and co-evaporated with toluene. Then methyl iodide (70 mL)was added and the reaction mixture was stirred overnight at roomtemperature. The solvent was evaporated and then several timesco-evaporated with dichloro-methane. Crude product was extracted withethyl acetate (100 mL) and 1 M aqueous solution of hydrochloric acid (50mL), water (50 mL) and brine (50 mL). Organic layer was separated, driedover anhydrous sodium sulfate, filtered and evaporated. The crudeproduct was purified by column chromatography (Silicagel, 0.063-0.200mm; eluent: cyclohexane/ethyl acetate 9:1) to provide methyl3-bromo-4-methyl-5-(methylthio)benzoate (2) as white solid. Yield: 1.83g (84%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.01 (d, J=1.3 Hz, 1H); 7.75(s, 1H); 3.93 (s, 3H); 2.53 (s, 3H); 2.50 (s, 3H).

Hydrogen peroxide (5 mL) was added to a solution of methyl3-bromo-4-methyl-5-(methylthio)benzoate (2, 1.83 g, 6.65 mmol) in aceticacid (70 mL) and the reaction mixture was allowed to stir at 70° C. for2 hours. The solvents were then evaporated to provide methyl3-bromo-4-methyl-5-(methylsulfonyl)benzoate (3) as off-white solid.

Yield: 2.05 g (100%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 8.46 (d, J=1.7 Hz, 1H); 8.40(d, J=1.8 Hz, 1H); 3.91 (s, 3H); 3.34 (s, 3H); 2.79 (s, 3H).

Solution of 1-bromopyrrolidine-2,5-dione (NBS, 1.31 g, 7.35 mmol),3-bromo-4-methyl-5-(methylsulfonyl)benzoate (3, 2.05 g, 6.65 mmol) and2,2-azobis(2-methylpropionitrile) (AIBN, 55.0 mg, 0.33 mmol) in PhCF₃(20 mL) was stirred overnight at 85 C. Reaction mixture was evaporatedand then extracted with diethyl ether (2×50 mL). Organic layers werewashed with brine (50 mL). Organic layer was separated, dried overanhydrous sodium sulfate, filtered and evaporated to provide methyl3-bromo-4-(bromomethyl)-5-(methylsulfonyl)benzoate (4) as yellowishsolid. Yield: 2.43 g (94%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 8.47 d, J=1.1 Hz, 2H); 5.14(bs, 2H); 3.92 (s, 3H); 3.44 (s, 3H).

Methyl 3-bromo-4-(bromomethyl)-5-(methylsulfonyl)benzoate (4, 2.70 g,7.00 mmol) was stirred with potassium acetate (1.37 g, 14.0 mmol) inacetonitrile (70 mL) at 75 C overnight. The suspension was filteredthrough Celite pad and evaporated in vacuo. The crude product wasdissolved in dichloromethane and filtered again. The filtrate wasevaporated and purified by column chromatography (Silicagel 60,0.040-0.063 mm; eluent: cyclohexane/ethyl acetate 7:1) to give methyl4-(acetoxymethyl)-3-bromo-5-(methylsulfonyl)benzoate (5) as white solid.Yield: 4.24 g (54%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.74 (s, 1H); 8.55 (s, 1H);5.76 (s, 2H); 3.99 (s, 3H); 3.21 (s, 3H); 2.11 (s, 3H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 30:70 to100:0+0.1% FA): 2.46 min.

LC-MS m/z: 366.9 (M+H)⁺.

A mixture of methyl4-(acetoxymethyl)-3-bromo-5-((trifluoromethyl)sulfonyl)benzoate (5, 1.97g, 5.38 mmol), bis(pinacolato)diboron (1.64 g, 6.46 mmol) and drypotassium acetate (1.58 g, 16.1 mmol) and[1,1-bis(diphenylphosphino)ferrocene]-dichloropalladium-dichloromethanecomplex (220 mg, 269 mol) were suspended in dry, degassed 1,4-dioxane(20 mL). Reaction mixture was stirred under nitrogen atmosphere at 90°C. overnight. The crude reaction mixture was then taken up in ethylacetate (60 mL) and filtered through a short pad of silica gel (20 g)topped with Celite (with the aid of ethyl acetate, 3×60 mL). Thefiltrate was evaporated in vacuo to give crude methyl4-(acetoxymethyl)-3-(methylsulfonyl)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate(6) a yellowish solid.

It was dissolved in tetrahydrofuran (15 mL) and water (15 mL) and solidlithium hydroxide monohydrate (1.13 g, 26.9 mmol) was added. The mixturewas stirred at room temperature for 2 hours and then diluted with water(60 mL) and transferred into a separatory funnel, where it was extractedwith dichloromethane (2×40 mL) and diethyl ether (40 mL). Aqueous phasewas acidified with concentrated hydrochloric acid to pH=2 and theresulting mixture was stirred for 30 minutes at room temperature. Theprecipitate was filtered, washed well with water and dried to give1-hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (7) as off-white solid. Yield: 1.20 g (87%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂O, δ_(H)): 8.67 (s, 1H); 8.54 (s,1H); 5.40 (s, 2H); 3.23 (s, 3H).

LC-MS purity: 100% (ELSD, UV 240 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 10:90 to100:0+0.1% FA): 2.10 min.

LC-MS m/z: 255.2 (M−H)⁻.

1-Hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (7, 1.02 g, 4.00 mmol), 2,3,4,5,6-pentrafluorophenol (1030 mg, 5.60mmol) and N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride(1.07 g, 5.60 mmol) were suspended in dichloromethane (20 mL) andacetonitrile (10 mL). The mixture was stirred overnight at roomtemperature. Then the solvent was evaporated. The residue was dissolvedin ethyl acetate (70 mL) and washed with water (2×40 mL) and brine (1×40mL). Organic layer was dried over anhydrous sodium sulfate, filtered andevaporated. The crude product was dissolved in hot ethyl acetate (10 mL)and cyclohexane (30 mL) was slowly added. After cooling to ambienttemperature, the solid precipitated. After 2 hours, it was collected byfiltration, washed with cyclohexane and air dried to giveperfluorophenyl1-hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(8) as off-white solid. Yield: 1.65 mg (98%).

¹H NMR spectrum (300 MHz, Acetone-d₆/D₂O, δ_(H)): 8.88 (s, 1H); 8.73 (s,1H); 5.49 (s, 2H); 3.30 (s, 3H).

¹⁹F NMR spectrum (282 MHz, Acetone-d₆/D₂O, δ_(F)): −154.63 (d, J=17.0Hz); −159.62 (t, J=21.3 Hz); 164.43 (t, J=19.1 Hz).

LC-MS purity: 100% (ELSD, UV 240 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 10:90 to100:0+0.1% FA): 3.44 min.

LC-MS m/z: 421.0 (M−H)⁻.

Perfluorophenyl1-hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(8, 422 mg, 1.00 mmol) and (2-aminoethyl)glycine (9, 59.0 mg, 0.50 mmol)were dissolved in N,N-dimethylformamide/water mixture (2:1, 3 mL).Triethylamine (500 L) was then added and the resulting mixture wasstirred overnight at room temperature. Afterwards, it was acidified with1 M aqueous solution of potassium bisulfate (15 mL) and extracted withethyl acetate (3×15 mL). The organic layer was dried over anhydroussodium sulfate, filtered and evaporated. The residue was co-distilledwith toluene (3×10 mL) and triturated with diethyl ether (3 mL). Theprecipitate was filtered, washed with diethyl ether (2×2 mL) and airdried. The obtained powder was purified by preparative LC/MS (SunFirePrep C18 OBD, 5m, 19×100 mm, acetonitrile/water 5:95 to 100:0+0.1% FA)and freeze-dried to give the titleN-(1-hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine(10) as colorless solid. Yield: 99.0 mg (32%).

¹H NMR spectrum (300 MHz, AcOD-d₄, δ_(H)): 8.74-8.46, 1H); 8.35 (app. d,1H); 8.06 (app. d, 1H); 7.96 (bs, 1H); 5.49-5.32 (m, 4H); 4.39 (app. d,2H); 4.03-3.61 (m, 4H); 3.21-3.03 (m, 6H).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.14 min.

LC-MS m/z: 595.0 (M+H)⁺.

Example 42N-(1-Hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo-[c][1,2]oxaborole-6-carboxamido)ethyl)glycine

N-(1-Hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo-[c][1,2]oxaborole-6-carboxamido)ethyl)glycinewas synthesized according to the reaction scheme shown in Chem. 47 andfollowing the procedure described below.

N-Iodosuccinimide (NIS, 61.5 g, 274 mmol) was added to a solution of3-bromo-4-methylbenzoic acid (1, 56.0 g, 260 mmol) in concentratedsulfuric acid (1 L) and the reaction mixture was allowed to stir atambient temperature for 16 hours. The reaction mixture was then pouredinto ice-water (2 L). Resulting mixture was poured onto ice bath (2 L),precipitate was filtered, washed with water and dried in vacuo toprovide 3-bromo-5-iodo-4-methylbenzoic acid (2) as off-white solid.Yield: 87.8 g (99%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 8.30 (d, J=1.7 Hz, 1H); 8.06(d, J=1.7 Hz, 1H); 2.64 (s, 3H).

Concentrated sulfuric acid (35 mL) was added to a solution of3-bromo-5-iodo-4-methylbenzoic acid (2, 55.4 g, 162 mmol) in methanol(1.5 L) and the reaction mixture was allowed to stir under refluxovernight. The reaction mixture was then evaporated under reducedpressure, dissolved in diethyl ether (1 L), washed with water (2×500 mL)and saturated aqueous solution of potassium carbonate (500 mL). Organiclayer was separated, dried over anhydrous sodium sulfate, filtered andevaporated to provide methyl 3-bromo-5-iodo-4-methylbenzoate (3) aswhite solid.

Yield: 50.0 g (87%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)) 8.32 (d, J=1.7 Hz, 1H); 8.09(d, J=1.3 Hz, 1H); 3.86 (s, 3H); 2.65 (s, 3H).

Mixture of methyl 3-bromo-5-iodo-4-methylbenzoate (3, 15.1 g, 42.5mmol), thiobenzoic acid (6.00 mL, 51.0 mmol), copper(I) iodide (0.81 g,4.25 mmol), N,N-diisopropylethylamine (14.8 mL, 85.0 mmol) and1,10-phenanthroline (1.53 g, 8.50 mmol) in dry toluene (120 mL) wasstirred under nitrogen atmosphere at 100° C. overnight. After coolingdown the suspension was filtered through celite pad and the solvent wasevaporated. The residue was purified by 2 rounds of flash columnchromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/dichloromethane 1:1) to give methyl3-(benzoylthio)-5-bromo-4-methylbenzoate (4) as off-white solid. Yield:14.9 g (96%).

R_(F) (SiO₂, cyclohexane/dichloromethane 1:1): 0.30.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.33 (d, J=1.7 Hz, 1H); 8.14(d, J=1.8 Hz, 1H); 8.08-8.00 (m, 2H); 7.69-7.61 (m, 1H); 7.56-7.49 (m,2H); 3.93 (s, 3H); 2.59 (s, 3H).

Mixture of methyl 3-(benzoylthio)-5-bromo-4-methylbenzoate (4, 8.81 g,24.1 mmol) and potassium carbonate (6.66 g, 48.2 mmol) in dry methanol(100 mL) was stirred under nitrogen atmosphere at room temperature for 1hour. The solvent was evaporated and co-evaporated with toluene. Thenpotassium carbonate (19.9 g, 145 mmol) and N,N-dimethylformamide (130mL) were added and the suspension was degassed and trifluoromethyliodide was added (using balloon filled with trifluoromethyl iodide). Themixture was stirred for 1.5 hours under 100 W light bulb and thenovernight at room temperature. Ethyl acetate (400 mL) was added and themixture was washed with water (2×300 mL), 1 M aqueous solution ofhydrochloric acid (1×300 mL) and brine (1×300 mL). Organic layer wasdried over anhydrous sodium sulfate, filtered and evaporated. Theresidue was purified by flash column chromatography (Silicagel 60,0.040-0.063 mm; eluent: cyclohexane/ethyl acetate 4:1) to give methyl3-bromo-4-methyl-5-((trifluoromethyl)thio)benzoate (5) as colorless oilwhich crystallized in fridge. Yield: 4.78 g (60%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 9:1): 0.65.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.35 (s, 1H); 8.31 (s, 1H);3.95 (s, 3H); 2.74 (s, 3H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −42.18 (s).

Methyl 3-bromo-4-methyl-5-((trifluoromethyl)thio)benzoate (5, 4.75 g,14.5 mmol) was dissolved in dichloromethane (20 mL) followed by additionof acetonitrile (20 mL), water (40 mL) and sodium periodate (9.29 g,43.4 mmol). Then ruthenium(III) chloride hydrate (52.0 mg) was added at0 C. The mixture was stirred for 2 hours at room temperature. Water (40mL) was added and the mixture was extracted with dichloromethane (2×80mL). Organic layers were combined, washed with 10% aqueous solution ofhydrogen peroxide (1×30 mL) dried over anhydrous sodium sulfate,filtered through celite pad and evaporated. The residue was purified byflash column chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/ethyl acetate 4:1) to give methyl3-bromo-4-methyl-5-((trifluoromethyl)sulfonyl)benzoate (6) as whitecrystals. Yield: 5.14 g (98%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 9:1): 0.45.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.73 (d, J=1.8 Hz, 1H); 8.63(d, J=1.7 Hz, 1H); 3.99 (s, 3H); 2.87 (s, 3H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −77.13 (s).

A mixture of methyl3-bromo-4-methyl-5-((trifluoromethyl)sulfonyl)benzoate (6, 5.13 g, 14.2mmol), N-bromosuccinimide (3.28 g, 18.5 mmol) and2,2-azobis(2-methylpropionitrile) (AIBN, 0.23 g, 1.42 mmol) inbenzotrifluoride (25 mL) was stirred at 85° C. overnight. Fullconversion was not achieved therefore N-bromosuccinimide (1.09 g, 6.17mmol) and 2,2-azobis(2-methylpropionitrile) (AIBN, 0.23 g, 1.42 mmol)were added and the mixture was stirred at 85° C. overnight.Dichloromethane (100 mL) was added and the mixture was washed with water(3×100 mL). Organic layer was dried over anhydrous sodium sulfate,filtered and evaporated. The residue was dissolved in acetonitrile (75mL) and potassium acetate (1.39 g, 14.2 mmol) was added. The mixture wasstirred at 75° C. overnight. The insoluble material was filtered off andthe filtrate was evaporated. The residue was purified by flash columnchromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/dichloromethane 2:1 to 1:1) to give methyl4-(acetoxymethyl)-3-bromo-5-((trifluoromethyl)sulfonyl)benzoate (7) aswhite powder.

Yield: 4.76 g (80%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 4:1): 0.35.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.78 (d, J=1.7 Hz, 1H); 8.70(d, J=1.7 Hz, 1H); 5.63 (s, 2H); 4.02 (s, 3H); 2.11 (s, 3H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −77.08 (s).

A mixture of methyl4-(acetoxymethyl)-3-bromo-5-((trifluoromethyl)sulfonyl)benzoate (7, 4.75g, 11.3 mmol), bis(pinacolato)diboron (3.74 g, 14.7 mmol) and drypotassium acetate (5.56 g, 56.6 mmol) in dry 1,4-dioxane (60 mL) wasdegassed; then [1,1-bis(diphenylphosphino)ferrocene]dichloropalladium(0.42 g, 0.57 mmol) was added. Reaction mixture was stirred undernitrogen atmosphere at 80° C. overnight. The solvent was evaporated. Theresidue was filtered through a short silica gel column indichloro-methane affording methyl4-(acetoxymethyl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-((trifluoromethyl)sulfonyl)benzoate(8) as yellow solid. Yield: 6.00 g.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.85 (s, 2H); 5.75 (s, 2H);4.00 (s, 3H); 2.05 (s, 3H); 1.37 (s, 12H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −77.39 (s).

Methyl4-(acetoxymethyl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-((trifluoromethyl)sulfonyl)benzoate(8, 0.47 g, 1.00 mmol) was dissolved in methanol (4 mL) and a solutionof lithium hydroxide monohydrate (0.21 g, 5.00 mmol) in water (2 mL) wasadded. The mixture was stirred for 35 minutes at room temperature thenit was extracted with diethyl ether (2×10 mL). Aqueous phase wasacidified with concentrated hydrochloric acid (434 L) and resultingmixture was stirred for 30 minutes at room temperature. The precipitatewas filtered, washed with water and dried to give1-hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (9) as white solid. Yield: 195 mg (63%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.85 (s, 1H); 8.88 (s, 1H);8.49 (s, 1H); 5.35 (s, 2H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −78.52 (s).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.69 min.

LC-MS m/z: 310.0 (M−H)⁻.

1-Hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylicacid (9, 195 mg, 0.63 mmol) was dissolved intetrahydrofuran/dichloromethane mixture (1:1, 10 mL) followed byaddition of 2,3,4,5,6-pentrafluorophenol (116 mg, 0.63 mmol) andN-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (121 mg,0.63 mmol). The mixture was stirred overnight at room temperature. Thenthe solvent was evaporated. The residue was dissolved in ethyl acetate(70 mL) and washed with water (2×40 mL) and brine (1×40 mL). Organiclayer was dried over anhydrous sodium sulfate, filtered and evaporatedto dryness to give perfluorophenyl1-hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxylate(10) as pale pink powder. Yield: 300 mg (100%).

¹H NMR spectrum (300 MHz, DMSO-d₆, δ_(H)): 9.93 (s, 1H); 9.09 (s, 1H);8.65 (s, 1H); 5.41 (s, 2H).

Perfluorophenyl1-hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo-[c][1,2]oxaborole-6-carboxylate(10, 238 mg, 0.50 mmol) and (2-aminoethyl)glycine (11, 29.5 mg, 0.25mmol) were dissolved in N,N-dimethylformamide/water mixture (2:1, 1.5mL). Triethylamine (250 L) was then added and the resulting mixture wasstirred overnight at room temperature. Afterwards, it was acidified with1 M aqueous solution of potassium bisulfate (15 mL) and extracted withethyl acetate (3×15 mL). The organic layer was dried over anhydroussodium sulfate, filtered and evaporated. The residue was co-distilledwith toluene (3×10 mL) and triturated with diethyl ether (3 mL). Theprecipitate was filtered, washed with diethyl ether (2×1 mL) and airdried. The obtained powder was dissolved in acetonitrile/water mixture(2:1, 20 mL) and freeze-dried to give the titleN-(1-hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo-[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine(12) as colorless solid.

Yield: 120 mg (68%).

¹H NMR spectrum (300 MHz, AcOD-d₆, 80 C, δ_(H)): 8.68 bs, 1H); 8.53 (bs,1H); 8.27 (s, 1H); 8.10 (s, 1H); 5.46 (s, 2H); 5.42 (s, 2H); 4.44-4.29(m, 2H); 3.99-3.72 (m, 4H).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 5.06 min.

LC-MS m/z: 702.1 (M+H)⁺.

Example 434-Borono-2-((3-borono-5-(trifluoromethyl)phenyl)sulfonyl)-6-(trifluoromethyl)benzoicacid

4-Borono-2-((3-borono-5-(trifluoromethyl)phenyl)sulfonyl)-6-(trifluoromethyl)benzoicacid was synthesized according to the reaction scheme shown in Chem. 48and following the procedure described below.

Mixture of 2-fluoro-6-(trifluoromethyl)benzoic acid (1, 1.00 g, 4.81mmol), di-tert-butyl dicarbonate (1.47 g, 6.73 mmol),4-(dimethylamino)pyridine (0.18 g, 1.44 mmol) and tert-butanol (5 mL) intetrahydrofuran (10 mL) was stirred overnight at room temperature. Themixture was diluted with ethyl acetate (40 mL) and washed with water(1×40 mL), 1 M aqueous solution of hydrochloric acid (1×40 mL), 5%aqueous solution of sodium carbonate (1×40 mL), water (1×40 mL) andbrine (1×40 mL). Organic layer was dried over anhydrous sodium sulfate,filtered and evaporated to dryness to give tert-butyl2-fluoro-6-(trifluoromethyl)benzoate (2) as colorless oil. Yield: 0.77 g(60%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.53-7.44 (m, 2H); 7.36-7.29(m, 1H); 1.60 (s, 9H).

Mixture of ester (2, 0.76 g, 2.87 mmol), 3-(trifluoromethyl)benzenethiol(3, 0.61 g, 3.44 mmol) and potassium carbonate (0.87 g, 6.31 mmol) inN,N-dimethylformamide (30 mL) was stirred under nitrogen atmosphereovernight at 100° C. Reaction mixture was then diluted with ethylacetate (30 mL) and washed with water (3×30 mL). Organic layer was driedover anhydrous sodium sulfate, filtered and evaporated to afford mixtureof starting ester (2) and tert-butyl2-(trifluoromethyl)-6-((3-(trifluoromethyl)phenyl)-thio)benzoate (4)(1:1.8). This mixture was dissolved in acetic acid (20 mL) and hydrogenperoxide (2 mL) was added. Resulting mixture was stirred at 70° C. for 7hours. Reaction mixture was then diluted with ethyl acetate (30 mL) andwashed with water (3×30 mL). Organic layer was dried over anhydroussodium sulfate, filtered and evaporated. The residue was purified byflash column chromatography (Silicagel 60, 0.040-0.063 mm; eluent:cyclohexane/ethyl acetate 4:1) to yield tert-butyl2-(trifluoromethyl)-6-((3-(trifluoromethyl)phenyl)sulfonyl)benzoate (5)as white powder.

Yield: 0.25 g (19%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 4:1): 0.45.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.37 (d, J=8.1 Hz, 1H);8.27-8.18 (m, 2H); 7.95 (d, J=7.7 Hz, 1H); 7.86 (d, J=7.9 Hz, 1H);7.77-7.64 (m, 2H); 1.67 (s, 9H).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 3.39 min.

LC-MS m/z: 477.3 (M+N_(a))⁺.

The sulfone (5, 0.25 g, 0.55 mmol), bis(pinacolato)diboron (350 mg, 1.38mmol), (1,5-cyclooctadiene)(methoxy)iridium(I) dimer (11.0 mg, 0.02mmol) and 4,4-di-tert-butyl-2,2-dipyridyl (dtbpy, 10.0 mg, 0.04 mmol)were dissolved in degassed tetrahydrofuran (5 mL) under nitrogen. Theresulting mixture was warmed to 50° C. and heated at this temperatureovernight. The mixture was evaporated to dryness; and the residuepurified by quick flash column chromatography (Silicagel 60, 0.040-0.063mm; eluent: dichloromethane) to give tert-butyl4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-((3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)sulfonyl)-6-(trifluoromethyl)benzoate(6) as white foam. Yield: 240 mg (62%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.75 (s, 1H); 8.52 (s, 1H);8.34 (s, 1H); 8.31 (s, 1H); 8.24 (s, 1H); 1.66 (s, 9H); 1.38 (s, 12H);1.36 (s, 12H).

Trifluoroacetic acid (5 mL) was added to a solution of tert-butyl4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-((3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)sulfonyl)-6-(trifluoromethyl)benzoate(6, 235 mg, 0.33 mmol) in dichloromethane (1 mL) and the mixture wasstirred for 2 hours at room temperature. The mixture was evaporated todryness in vacuo, and the residue was evaporated from dichloromethane(5×10 mL) to afford4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2-((3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethyl)phenyl)sulfonyl)-6-(trifluoromethyl)benzoicacid (7) as white foam. Yield: 214 mg (100%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.78 (s, 1H); 8.60 (s, 1H);8.34 (s, 2H); 8.25 (s, 1H); 1.39 (s, 12H); 1.36 (s, 12H).

A solution of the above acid (7, 210 mg, 0.33 mmol) in acetonitrile (4mL) was diluted with water (1 mL) followed by addition of periodic acid(301 mg, 1.32 mmol). The resulting mixture was stirred for 1 hour; andthen it was partitioned between ethyl acetate (30 mL) and water (30 mL).The phases were separated; the organic one was washed with water (1×30mL) and brine (1×30 mL); dried over anhydrous sodium sulfate, filteredand evaporated to dryness. The residue was dissolved in 20% aqueoussolution of sodium hydroxide (10 mL) and washed with dichloromethane(2×40 mL). The aqueous layer was acidified with 1 M aqueous solution ofhydrochloric acid (30 mL) and extracted with ethyl acetate (2×50 mL).Ethyl acetate extracts were combined, dried over anhydrous sodiumsulfate, filtered and concentrated in vacuo until the product started toprecipitate. The suspension was diluted with n-hexane (50 mL). Theprecipitate was collected by filtration, washed with n-hexane, dissolvedin acetonitrile (30 mL) and freeze-dried to afford the title compound(8) as beige powder. Yield: 138 mg (88%).

¹H NMR spectrum (300 MHz, DMSO-d₆/DCl, δ_(H)): 8.86 (s, 1H); 8.62 (s,1H); 8.42 (s, 1H); 8.37 (s, 1H); 8.26 (s, 1H).

¹⁹F NMR spectrum (282 MHz, DMSO-d₆, δ_(F)): −58.17 (s); −61.40 (s).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 20:80 to100:0+0.1% FA): 4.05 min.

LC-MS m/z: 467.9 (M−H₂O+H)⁺.

Example 442-((Bis(3-borono-5-(trifluoromethoxy)phenyl)(oxo)-λ6-sulfanylidene)amino)aceticacid

2-((Bis(3-borono-5-(trifluoromethoxy)phenyl)(oxo)-λ6-sulfanylidene)amino)aceticacid was synthesized according to the reaction scheme shown in Chem. 49and following the procedure described below.

A solution of 1-iodo-3-(trifluoromethoxy)benzene (1, 9.08 g, 31.5 mmol)in N,N-dimethylformamide (63 mL) was added to sodium sulfide nonahydrate(5.30 g, 22.1 mmol) and potassium carbonate (4.36 g, 31.5 mmol) in apressure reactor. The mixture was degassed and backfilled with argon.Cuprous iodide (600 mg, 3.15 mmol) was added, the reactor was sealed andheated to 120° C. The mixture was heated at 120° C. for 3 days, then itwas cooled to room temperature and diluted with diethyl ether (100 mL).The resulting mixture was filtered over Celite. The filtrate was washedwith water (150 mL), and the aqueous layer was re-extracted with diethylether (2×100 mL). All organic fractions were combined, washed 1 Maqueous solution of sodium hydroxide (2×100 mL), water (100 mL) andbrine (70 mL); dried over anhydrous sodium sulfate and evaporated todryness in vacuo. The residue was purified by flash columnchromatography (Silicagel 60, 0.040-0.063 mm; eluent: cyclohexane) togive bis(3-(trifluoromethoxy)-phenyl)sulfane (2) as colorless liquid.Yield: 5.04 g (90%).

R_(F) (SiO₂, cyclohexane/ethyl acetate 95:5): 0.45.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 7.41-7.33 (m, 2H); 7.30-7.25(m, 2H); 7.20 (s, 20H); 7.18-7.12 (m, 2H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −57.91 (s).

LC-MS purity: 97% (UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 70:30 to100:0+0.1% FA): 3.48 min.

LC-MS m/z: 355.2 (M+H)⁺.

(Diacetoxyiodo)benzene (PIDA, 12.8 g, 39.7 mmol) was added to a mixtureof bis(3-(trifluoromethoxy)phenyl)sulfane (2, 5.63 g, 15.9 mmol) andpowdered ammonium carbamate (2.48 g, 31.8 mmol) in methanol (32 mL). Theresulting pale yellow solution was stirred at room temperature for 3hours, and then it was evaporated to dryness in vacuo. A solution ofpotassium carbonate (12.5 g) and sodium thiosulfate (25 g) in water (200mL) was added to the residue, followed by ethyl acetate (200 mL). Thephases were separated and the aqueous one was extracted with ethylacetate (3×100 mL). The organic fractions were combined, dried overanhydrous sodium sulfate and evaporated in vacuo. The residue waspurified by flash column chromatography (Silicagel 60, 0.040-0.063 mm;eluent: cyclohexane/ethyl acetate 95:5 to 70:30) to giveiminobis(3-(trifluoromethoxy)phenyl)-λ⁶-sulfanone (3) as pale yellowliquid. Yield: 5.38 g (88%).

R_(F) (SiO₂, n-hexane/ethyl acetate 1:1): 0.45.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.00-7.94 (m, 2H); 7.92 (s,2H); 7.56 (t, J=8.1 Hz, 2H); 7.45-7.38 (m, 2H); 3.20 (bs, 1H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)): −58.00 (s).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 3.78 min.

LC-MS m/z: 386.3 (M+H)⁺.

Sodium hydride (60% dispersion in mineral oil, 614 mg, 15.4 mmol) wasadded to a solution of iminobis(3-(trifluoromethoxy)phenyl)-6-sulfanone(3, 5.38 g, 14.0 mmol) in dry N,N-dimethylformamide (42 mL) and themixture was stirred at room temperature for 1 hour. tert-Butylbromoacetate (4.68 mL, 21.0 mmol) was added; the mixture was heated to60° C. and stirred at this temperature for 3 hours. The mixture wascooled to room temperature, diluted with 10% aqueous solution ofpotassium hydrogensulfate (200 mL) and extracted with ethyl acetate(2×100 mL). Separated organic layers were combined, washed with water(4×150 mL) and brine (100 mL); dried over anhydrous sodium sulfate andevaporated in vacuo. The residue was subjected to flash columnchromatography (Silicagel 60, 0.040-0.063 mm; eluent: cyclohexane/ethylacetate 95:5) to give pure fraction of tert-butyl2-((oxobis(3-(trifluoromethoxy)phenyl)-λ⁶-sulfanylidene)amino)acetate(4) as colorless oil. Yield: 5.51 g (79%).

R_(F) (SiO₂, n-hexane/ethyl acetate 1:1): 0.60.

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)): 8.02-7.96 (m, 2H); 7.93 (s,2H); 7.56 (d, J=8.0 Hz, 2H); 7.44-7.38 (m, 2H); 3.77 (s, 2H); 1.48 (s,9H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)) −57.99 (s).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 35:65 to100:0+0.1% FA): 4.88 min.

LC-MS m/z: 500.4 (M+H)⁺.

tert-Butyl2-((oxobis(3-(trifluoromethoxy)phenyl)-λ⁶-sulfanylidene)amino)acetate(4, 810 mg, 1.62 mmol), bis(pinacolato)diboron (906 mg, 3.57 mmol),(1,5-cyclooctadiene)(methoxy)iridium(I) dimer (10.8 mg, 16.2 μmol) and4,4-di-tert-butyl-2,2-dipyridyl (dtbpy, 10.9 mg, 40.5 μmol) weredissolved in degassed tetrahydrofuran (3.2 mL) under argon. Theresulting mixture was warmed to 70° C. and heated at this temperaturefor 5 hours. The mixture was evaporated to dryness and re-dissolved indichloromethane (20 mL). Methanol (40 mL) was added; the solution wasstirred for 30 minutes, and then it was evaporated in vacuo. The residuewas purified by flash column chromatography (Silicagel 60, 0.040-0.063mm; eluent: dichloromethane/ethyl acetate 10:0 to 4:1) to givetert-butyl2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethoxy)phenyl)-26-sulfanylidene)amino)acetate(5) as pale orange foam. Yield: 1.15 g (95%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)) 8.32 (s, 2H); 8.03 (s, 2H); 7.79(s, 2H); 3.76 (s, 2H); 1.51 (s, 9H); 1.34 (s, 24H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)) −57.87 (s).

LC-MS purity: 92% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 85:15 to100:0+0.1% FA): 4.63 min.

LC-MS m/z: 752.9 (M+H)⁺.

Trifluoroacetic acid (6 mL) was added to a solution of tert-butyl2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethoxy)phenyl)-_6-sulfanylidene)-amino)acetate(5, 1.14 g, 1.52 mmol) in dichloromethane (3.00 mL) and the mixture wasstirred for 2 hours at room temperature. The mixture was evaporated todryness in vacuo, and the residue was evaporated from toluene (3×20 mL)and dichloromethane (3×20 mL). The residue was dissolved in 0.5 Maqueous solution of sodium hydroxide (30 mL). The resulting cloudysolution was washed with dichloromethane (2×10 mL), acidified with 1 Maqueous solution of hydrochloric acid (20 mL) and extracted with ethylacetate (3×25 mL). Combined ethyl acetate extracts were dried overanhydrous sodium sulfate and evaporated in vacuo to give2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethoxy)phenyl)-26-sulfanylidene)amino)aceticacid (6) as off-white foam. Yield: 1.06 g (100%).

¹H NMR spectrum (300 MHz, CDCl₃, δ_(H)) 8.27 (s, 2H); 7.92 (s, 2H); 7.85(s, 2H); 3.85 (s, 2H); 1.36 (s, 12H); 1.35 (s, 12H).

¹⁹F NMR spectrum (282 MHz, CDCl₃, δ_(F)) −57.92 (s).

LC-MS purity: 100% (ELSD).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 85:15 to100:0+0.1% FA): 0.89 min (M-pinacol), 2.23 min (M).

LC-MS m/z: 614.6 (M-pinacol+H)⁺, 696.8 (M+H)⁺.

A solution of2-((oxobis(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5-(trifluoromethoxy)phenyl)-λ⁶-sulfanylidene)amino)aceticacid (6, 1.06 g, 1.52 mmol) in acetonitrile (10.7 mL) was diluted withwater (2.1 mL) followed by addition of periodic acid (1.39 g, 6.08mmol). The resulting mixture was stirred for 1 hour; and then it waspartitioned between ethyl acetate (240 mL) and water (60 mL). The phaseswere separated; the organic one was washed with saturated aqueoussolution of potassium chloride (2×100 mL); dried over anhydrous sodiumsulfate and evaporated to dryness. The residue was dissolved in 0.5 Maqueous solution of sodium hydroxide (60 mL) and washed withdichloromethane (3×60 mL). The aqueous layer was acidified with 1 Maqueous solution of hydrochloric acid (60 mL) and extracted with ethylacetate (2×120 mL). Ethyl acetate extracts were combined, dried overanhydrous sodium sulfate and concentrated in vacuo until the productstarted to precipitate (approx. 20 mL volume). The suspension wasdiluted with n-hexane (50 mL) and placed into a fridge for 1 hour. Theprecipitate was collected by filtration, washed with n-hexane (3×10 mL)and dried in vacuo to give 623 mg of crude title compound (7). A portionof the precipitate (210 mg) was purified by preparative HPLC (SunFirePrep C18 OBD, 5m, 19×100 mm, acetonitrile/water 5:95 to 100:0+0.1% FA)and freeze-dried to afford the title compound (7) as white powder.Yield: 146 mg (53%).

¹H NMR spectrum (300 MHz, DMSO-d₆+DCl, δ_(H)): 8.34 (dd, J=1.7 and 0.7Hz, 2H); 7.98 (s, 2H); 7.94 (s, 2H); 3.68 (s, 2H).

¹⁹F NMR spectrum (282 MHz, DMSO-d₆+DCl, δ_(F)): −56.99 (s).

LC-MS purity: 100% (ELSD, UV 254 nm).

LC-MS Rt (Kinetex C18, 4.6 mm×50 mm, acetonitrile/water 5:95 to100:0+0.1% FA): 3.26 min.

LC-MS m/z: 532.0 (M+H)⁺.

Example 45: Carbohydrates and Diboronate Binding Affinity—the AlizarinAssay (ARS)

The alizarin-red binding assay is a colorimetric assay used to determinethe inhibition affinity of boronate compounds to glucose. The assay isbased on a colour shift of alizarin-red upon binding to boronate, whichshift can be followed by change in absorbance in the 330-340 nm region.

Determination of the Dissociation Constant (Kd)

For determination of the dissociation constant (Kd) between the AlizarinRed (ARS) and the boronate compound, 200 μM of ARS is dissolved in a 20mM of phosphate buffer pH 7.4, and titrated in triplicate into a 96 wellplate with 1, 0.5, 0.25, 0.125, 62.5, 31.25, 15.625, 7.812, 3.906,1.953, 0.9767, 0.488 and 0.244 mM of boronic acid. After 5 minutes ofcentrifugation at 4000 rpm, the plate is placed in a multiwellspectrometer (SpectraMax, Molecular Devices) for absorption detection.

The analysis is carried out at room temperature with absorption readingsat 330, 340 and 520 nm, respectively. Data obtained for absorptionversus concentration of boronate is then fitted (Prism 7, GraphPad) witha sigmoidal function to obtain the Kd value of boronate and ARS.

Determination of the Displacement Constant (K_(d))

For determination of the inhibitory constant (Ki) between the boronateand the carbohydrate, 400 μM of boronic acids is dissolved in a 20 mMphosphate buffer pH 7.4 under gentle stirring. Upon complete dissolutionof the compound, 200 μM of Alizarin red (ARS) is added to the solution.The ARS-boronate solution is then aliquoted into a 96 multiwell plate(black, flat and clear bottom) 1:1 with appropriate carbohydrate. Inparticular, D-glucose and L-lactate solutions are prepared in a 20 mMphosphate buffer pH 7.4 at these concentrations respectively: 1000, 500,250, 100, 50, 25, 10, 5, 2.5, 1, 0.25, 0.1 mM and 2500, 1000, 500, 100,50, 10, 5, 1, 0.5, 0.1, 0.05, 0.01 mM. The plate with ARS-boronate mixedwith carbohydrate is incubated 20 minutes at room temperature. After 5minutes of centrifugation at 4000 rpm the plate is placed in a multiwellspectrometer (SpectraMax, Molecular Devices) for absorption detection.

The analysis is carried out at room temperature with absorption readingsat 330, 340 and 520 nm, respectively. Data obtained for absorptionversus concentration of carbohydrate is then fitted (Prism 7, GraphPad)with a one site Ki equation constrained for the value of Kd of theobtained for ARS-boronate and for the concentration of the ARS (100 μM)to obtain the Ki value of the boronate for the chosen carbohydrate.

Example 46: Glucose Affinity by ¹³C NMR Assay

The ¹³C Glucose assay is an NMR based assay that takes advantage of theslow chemical shift exchange between the unbound glucose (A state) andthe glucose bound to diboronates (B state). If

and the chemical shift difference between state A and B is Δω, theprocess is in slow exchange (on NMR time scale) when k_(ex)<<Δω

In a slow exchange regime NMR signals from both states (A and B) areobserved and reflect the distinct chemical shifts of the two states asthere is not significant intercon-version in the timescale of the NMRexperiments. Therefore the intensity of each peak directly reports onthe population of that state.

The dissociation constant (Kd) could be defined as Kd=([A][B])/[AB],given At as the total concentration of specie A and Bt as totalconcentration of specie B, in the case in which At˜Bt, the product atthe equilibrium AB is given by the following equation:

$\begin{matrix}{{AB} = \frac{\left( {{At} + {Bt} + {Kd}} \right) - \sqrt{\left( {{At} + {Bt} + {Kd}} \right)^{2} - {4({AtBt})}}}{2}} & (1)\end{matrix}$

so that knowing At, Bt and AB at the equilibrium is possible todetermine Kd. Binding of glucose to boronates happens in a NMR slowexchange regime so that is possible to de-fine the concentration of ABby investigating the intensities of the C13 Glucose peaks before andafter the binding of diboronates.

Determination of the Dissociation Constant (Kd)

For determination of the dissociation constant (Kd) between glucose andthe boronate compound, samples of 1 mM of glucose C13 with and without 1mM of boronate at pH 7.4 in 10 mM phosphate buffer and 5% D2O areprepared. The samples are then investigated with a standard Carbon HSQCin a Bruker NMR instrument (RT, 32 scans). The intensities of the peaksof free glucose and glucose bound to boronates are determined by the useof TOPSPIN program (Bruker). Difference between intensity of freeglucose and glucose bound peaks gives the concentration of product AB atthe equilibrium so that Kd can be calculated using equation 1.

Data in table 1 show that the diboron compounds of the invention bindglucose with Kd values in the low millimolar range (0.2 to 4.5 mM), andthat the diboron compounds of the invention have higher affinity towardsglucose than towards lactacte.

TABLE 1 Glucose and lactate Kd-values as determined by the alizarinassay described in Example 45 for diboron compounds representative ofthe invention. Compound of Binding Affinity Binding Affinity Example No.Formula [Kd Glucose (mM)] [Kd Lactate (mM)] Example 1 Ia + IIa 3.1  8.6Example 2 Ia + IIa 3.4  5.4 Example 3 Ib + IIa 2.7 16.0 Example 4 Ic +IIa 2.6  6.5 Example 5 Ib + IIb 0.8 40.0 Example 6 Ia + IIb 1.1 N.D.Example 7 Ib + IIb 1.5 24.1 Example 8 Ib + IIb 2.7 34.0 Example 9 Ib +IIb 2.6 67.9 Example 10 Ic + IIb 3.2 352.0  Example 11 Ig + IIa 1.8 17.0Example 12 Ie + IIa 1.1 18.0 Example 13 Ie + IIa 0.3  4.0 Example 14Ic + IIb 3.2 16.0 Example 15 Ic + IIb 0.5 10.0 Example 16 Ic + IIb 4.237.0 Example 17 Ic + IIb 1.6 107.0  Example 18 Ih + IIa 0.4 13.0 Example19 Ie + IIa 1.5 17.0 Example 20 Ig + IIa 1.7 31.0 Example 21 Id + IIb2.6 N.D. Example 22 Ie + IIa 2.0 20.0 Example 24 Ig + IIa 1.2 34.0Example 25 Ib + IIb 1.3 11.0 Example 26 Ic + IIb 0.2 10.0 Example 27Id + IIb 1.1 41.0 Example 28 Ig + IIa 0.3 N.D. Example 29 Id + IIb 2.3230 Example 30  Ii + IIa 0.06* N.D. Example 31 Ib + IIb 0.8 100.0 Example 32 Ib + IIb 3.2 60.6 Example 33 Ic + IIb 4.5 152.7  Example 34 Ii + IIa 2.1 24.9 Example 35  Ii + IIa 0.6 20.0 Example 36  Ii + IIa2.3 20.0 Example 37 Ib + IIb 4.2 13.0 Example 38  Ii + IIb 3.7 N.D.Example 39 Ig + IIa 2.4 27.0 Example 40 Ic + IIb 2.0 N.D. Example 41Ib + IIb 1.4  4.4 Example 42 Ib + IIb 1.1 N.D. Example 43 Ig + IIa 0.722.0 Example 44  Ii + IIa 0.8 41.0 N.D. = not detectable. *measured by13C-NMR as described in Example 46

Example 47: Fluorine NMR Assay

This assay describes how to determine the ¹⁹F NMR spectrum, which showsdiboron compound binding to albumin, and glucose sensitive albuminbinding of the diboron compound.

Diboron compound is dissolved at a 0.1 mM concentration in a 50 mMphosphate buffer pH 7.4, 10% deuterated water (D2O), and mixed with 0,0.1, 0.2, 0.5, 1 and 2 mM human serum albumin (HSA). An additionalsample with diboron compound in the presence of 1 mM HSA and 50 mMglucose is prepared.

The samples are then placed into 3 mm standard NMR tube (Bruker) andtransferred for analysis to a 400 Mhz Bruker spectrometer equipped witha cryoprobe suitable for fluorine detection. The experiment is carriedout with standard Bruker zgflqn pulse sequence at room temperature withenough scans to have a S/N ratio over 50 for the 0 mM HSA sample. Thespectra are processed, visualized and compared by TopSpin program(Bruker).

The binding of diboron compound to HSA is qualitatively assessed bydecrease of the fluorine signal of the diboron compound upon binding toHSA. Release of the diboron compound from HSA upon addition of glucoseis assessed by re-appearance/increase of fluorine signal in the spectra.

F-NMR signals are depicted in FIG. 3, 4, 5, 6 and show that the diboroncompounds (exemplified by the diboron compounds of Example 3, 22, 25 and26) bind to albumin in a glucose-dependent manner.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

1. A diboron compound represented by Formula IR¹—X—R² in which Formula I, X represents a linker of Formula Ia:

wherein

represents a covalent bond towards R¹ or R²; W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing an L-gamma-Glu or a D-gamma-Glu residue); or Xrepresents a linker of Formula Ib:

wherein,

represents a covalent bond towards R¹ or R²; and R³ represent—(CH₂)_(m)(C═O)—W; wherein m represents an integer in the range of 1 to4; and W represents OH, NHCH₂COOH; NHCH₂CH₂COOH; NHCH₂CH₂CH₂COOH; orNHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); or X represents a linker of Formula Ic:

which represents a D- or an L-amino acid form; and wherein,

represents a covalent bond towards R¹ or R²; n represents an integer inthe range of 1 to 4; W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH,—NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latter representing anL-gamma-Glu or a D-gamma-Glu residue); or wherein X represents a linkerof Formula Id:

which represents a R,R or SS, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine; wherein,

represents a covalent bond towards R¹ or R²; R⁴ represents—(C═O)(CH₂)_(p)(C═O)—W; wherein p represents an integer in the range of1 to 4; W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH,or —NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); or X represents a linker of Formula Ie:

wherein,

represents a covalent bond towards R¹ or R²; or X represents a linker ofFormula If:

wherein,

represents a covalent bond towards R¹ or R²; or X represents a linker ofFormula Ig:

wherein,

represents a covalent bond towards R¹ or R²; or X represents a linker ofFormula Ih:

wherein,

represents a covalent bond towards R¹ or R²; or X represents a linker ofFormula Ii:

wherein,

represents a covalent bond towards R¹ or R²; and W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing an L-gamma-Glu or a D-gamma-Glu residue); andR¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein, one to four Y represents H; and none, one or two of Yrepresents F, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and one Yrepresents (a covalent bond representing) the attachment point to X ofFormula I; and when X is Formula Ie, If, Ig or Ih, one Y in either R¹ orR² represents —(C═O)—W, where W represents —OH, —NHCH₂COOH,—NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latterrepresenting an L-gamma-Glu or a D-gamma-Glu residue).
 2. The diboroncompound of claim 1, represented by Formula I, wherein X represents alinker of Formula Ia:

wherein,

represents a covalent bond towards R¹ or R²; W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing an L-gamma-Glu or a D-gamma-Glu residue); andR¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein, one Y represents (a covalent bond representing) the attachmentpoint to the linker X of Formula Ia; none, one or two of Y represent F,Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and the remaining Yrepresents H.
 3. The diboron compound of claim 1, represented by FormulaI, wherein X represents a linker of Formula Ib:

wherein,

represents a covalent bond towards R¹ or R²; and R³ represent—(CH₂)_(m)(C═O)—W; wherein m represents an integer in the range of 1 to4; W represents OH, NHCH₂COOH; NHCH₂CH₂COOH; NHCH₂CH₂CH₂COOH; orNHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and R¹ and R², which may be identical ordifferent, each represents a group of Formula IIa or IIb:

wherein, one Y represents (a covalent bond representing) the attachmentpoint to the linker X of Formula Ib; none, one or two of Y represent F,Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and the remaining Yrepresents H.
 4. The diboron compound of claim 1, represented by FormulaI, wherein X represents a linker of Formula Ic:

which represents a D- or an L-amino acid form; and wherein,

represents a covalent bond towards R¹ or R²; n represents an integer inthe range of 1 to 4; W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH,—NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latter representing anL-gamma-Glu or a D-gamma-Glu residue); and R¹ and R², which may beidentical or different, each represents a group of Formula IIa or IIb:

wherein, one Y represents (a covalent bond representing) the attachmentpoint to the linker X of Formula Ic; none, one or two of Y represent F,Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and the remaining Yrepresents H.
 5. The diboron compound of claim 1, represented by FormulaI, wherein X represents a linker of Formula Id:

which represents a R,R or SS, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine; wherein,

represents a covalent bond towards R¹ or R²; R⁴ represents—(C═O)(CH₂)_(p)(C═O)—W; wherein p represents an integer in the range of1 to 4; W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH,or —NHCH(COOH)CH₂CH₂COOH (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and R¹ and R², which may be identical ordifferent, each represents a group of Formula IIa or IIb:

wherein, one Y represents (a covalent bond representing) the attachmentpoint to the linker X of Formula Id; none, one or two of Y represent F,Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and the remaining Yrepresents H.
 6. The diboron compound of claim 1, represented by FormulaI, wherein X represents a linker of Formula Ie:

wherein,

represents a covalent bond towards R¹ or R²; and R¹ and R², which may beidentical or different, each represents a group of Formula IIa or IIb:

wherein, one Y represents (a covalent bond representing) the attachmentpoint to the linker —CO— of Formula Ie; one Y in either R¹ or R²represents —(C═O)—W, where W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH,—NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latter representing anL-gamma-Glu or a D-gamma-Glu residue); none, one or two of Y representF, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and the remaining of Yrepresents H.
 7. The diboron compound of claim 1, represented by FormulaI, wherein X represents a linker of Formula If:

wherein,

represents a covalent bond towards R¹ or R²; and R¹ and R², which may beidentical or different, each represents a group of Formula IIa or IIb:

wherein, one Y represents (a covalent bond representing) the attachmentpoint to the linker —SO— of Formula If; one Y in either R¹ or R²represents —(C═O)—W, where W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH,—NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latter representing anL-gamma-Glu or a D-gamma-Glu residue); none, one or two of Y representF, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and the remaining Yrepresents H.
 8. The diboron compound of claim 1, represented by FormulaI, wherein X represents a linker of Formula Ig:

wherein,

represents a covalent bond towards R¹ or R²; and R¹ and R², which may beidentical or different, each represents a group of Formula IIa or IIb:

wherein, one Y represents (a covalent bond representing) the attachmentpoint to the linker —(SO₂)— of Formula Ig; one Y in either R¹ or R²represents —(C═O)—W, where W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH,—NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latter representing anL-gamma-Glu or a D-gamma-Glu residue); none, one or two of Y representF, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and the remaining Yrepresents H.
 9. The diboron compound of claim 1, represented by FormulaI, wherein X represents a linker of Formula Ih:

wherein,

represents a covalent bond towards R¹ or R²; and R¹ and R², which may beidentical or different, each represents a group of Formula IIa or IIb:

wherein, one Y represents (a covalent bond representing) the attachmentpoint to the linker —(CF₂)— of Formula Ih; one Y in either R¹ or R²represents —(C═O)—W, where W represents —OH, —NHCH₂COOH, —NHCH₂CH₂COOH,—NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH (the latter representing anL-gamma-Glu or a D-gamma-Glu residue); none, one or two of Y representF, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and the remaining Yrepresents H.
 10. The diboron compound of claim 1, represented byFormula I, wherein X represents a linker of Formula Ii:

wherein,

represents a covalent bond towards R¹ or R²; W represents —OH,—NHCH₂COOH, —NHCH₂CH₂COOH, —NHCH₂CH₂CH₂COOH, or —NHCH(COOH)CH₂CH₂COOH(the latter representing an L-gamma-Glu or a D-gamma-Glu residue); andR¹ and R², which may be identical or different, each represents a groupof Formula IIa or IIb:

wherein, one Y represents (a covalent bond representing) the attachmentpoint to the linker X of Formula Ii; none, one or two of Y represent F,Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and the remaining Yrepresents H.
 11. A diboron compound selected from the group consistingof 3,5-Bis((4-borono-2-fluorobenzamido)methyl)benzoic acid;3,5-Bis((4-borono-3-fluorobenzamido)methyl)benzoic acid;N,N′-bis(4-borono-3-fluorobenzamido)-N-ethyl-glycine amide;(S)-2,4-bis(4-borono-3-fluorobenzamido)butanoic acid;N-(7-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;3,5-Bis((7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)methyl)benzoic acid;N-(5-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;N-(4-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;N-(6-Fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-N-(2-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carboxamido)ethyl)glycine;N²,N⁶-Bis(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-5-carbonyl)-L-lysine;3-Borono-5-((3-borono-4-fluorophenyl)sulfonyl)-4-fluorobenzoic acid;3-Borono-5-(3-borono-5-fluorobenzoyl)benzoic acid;3-Borono-5-(5-borono-2,4-difluorobenzoyl)benzoic acid;N⁶-(4-Borono-2-fluorobenzoyl)-N²-(6-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]-oxaborole-5-carbonyl)-L-lysine;(S)-2,3-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanoicacid;(S)-2,3-Bis(5-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanoicacid;(S)-2,3-Bis(4-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-propanoicacid;(3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)difluoromethyl)benzoyl)glycine;(3-Borono-5-(3-borono-5-(trifluoromethyl)benzoyl)benzoyl)glycine;(3-Borono-5-((3-borono-5-(trifluoromethyl)phenyl)sulfonyl)glycine;4-((3S,4S)-3,4-Bis(7-fluoro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoicacid; (3-Borono-5-(3-borono-5-fluorobenzoyl)benzoyl)glycine;(3-(6-Borono-2-(ethoxycarbonyl)-8-fluoro-1,1-dioxido-4H-benzo[b][1,4]thiazin-4-yl)-5-fluorophenyl)boronicacid; (3-Borono-5-((3-borono-5-fluorophenyl)sulfonyl)benzoyl)glycine;N-(1-Hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-ethyl)glycine;(S)-2,3-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid;4-((3S,4S)-3,4-Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)pyrrolidin-1-yl)-4-oxobutanoicacid;(3-Borono-5-((3-borono-5-(pentafluoro-λ⁶-sulfanyl)phenyl)sulfonyl)benzoyl)glycine;2-((Bis(3-borono-5-(trifluoromethyl)phenyl)(oxo)-16-sulfanylidene)amino)aceticacid;N-(4-(Difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-(difluoromethyl)-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-ethyl)glycine;N-(4-Chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;3-(2,3-Bis(4-chloro-1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanamido)propanoicacid;2-((Bis(3-borono-5-(difluoromethyl)phenyl)(oxo)-16-sulfanylidene)amino)aceticacid;2-((Bis(3-borono-5-chlorophenyl)(oxo)-16-sulfanylidene)amino)aceticacid; 2-((Bis(3-boronophenyl)(oxo)-16-sulfanylidene)amino)acetic acid;N-(1-Hydroxy-5-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-5-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-ethyl)glycine;2-((Bis(1-hydroxy-4-(trifluoromethyl)-1,3-dihydrobenzo[c][1,2]oxaborol-6-yl)(oxo)-16-sulfanylidene)amino)aceticacid; (3-Borono-5-((3-boronophenyl)sulfonyl)benzoyl)glycine;(S)-2,3-Bis(1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)propanoicacid;N-(1-Hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-(methylsulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carboxamido)-ethyl)glycine;N-(1-Hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-N-(2-(1-hydroxy-4-((trifluoromethyl)sulfonyl)-1,3-dihydrobenzo-[c][1,2]oxaborole-6-carboxamido)ethyl)glycine;4-Borono-2-((3-borono-5-(trifluoromethyl)phenyl)sulfonyl)-6-(trifluoromethyl)benzoicacid; and2-((Bis(3-borono-5-(trifluoromethoxy)phenyl)(oxo)-16-sulfanylidene)amino)aceticacid.
 12. A diboron conjugate, wherein the diboron compound according toclaim 1 is conjugated to a drug substance via an optional linker. 13.The diboron conjugate of claim 12, wherein the diboron compound isconjugated to the drug substance via an optional linker byderivatisation of the carboxylic acid moiety of the diboron compound.14. A diboron conjugate represented by the general Formula I′R¹′—X′—R²′ in which Formula I′, X′ represents a linker of Formula Ia′:

wherein,

represents a covalent bond towards R¹′ or R²′; D represents a drugsubstance; and W′ represents a covalent bond, or a linker selected fromthe group consisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—,—NHCH₂CH₂CH₂(C═O)—, and —NHCH(COOH)CH₂CH₂(C═O)— (the latter representingan L-gamma-Glu or a D-gamma-Glu residue); or X′ represents a linker ofFormula Ib′:

wherein,

represents a covalent bond towards R¹′ or R²′; and R³′ represent—(CH₂)_(m′)(C═O)—W′—D, wherein m′ represents an integer in the range of1 to 4; W′ represents a covalent bond or a linker selected from thegroup consisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—,and —NHCH(COOH)CH₂CH₂(C═O)— (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and D represents a drug substance; or X′represents a linker of Formula Ic′:

which represents a D- or an L-amino acid form; and wherein,

represents a covalent bond towards R¹′ or R²′; n′ represents an integerin the range of 1 to 4; W′ represents a covalent bond or a linkerselected from the group consisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—,—NHCH₂CH₂CH₂(C═O)—, and —NHCH(COOH)CH₂CH₂(C═O)— (the latter representingan L-gamma-Glu or a D-gamma-Glu residue); and D represents a drugsubstance; or X′ represents a linker of Formula Id′:

which represents a R,R or SS, or R,S or R,S stereoisomer of the3,4-diamino-pyrrolidine; wherein,

represents a covalent bond towards R¹′ or R²′; R⁴′ represents—(C═O)(CH₂)_(p′)(C═O)—W′—D; where W′ represents a covalent bond or alinker selected from the group consisting of —NHCH₂(C═O)—,—NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, and —NHCH(COOH)CH₂CH₂(C═O)— (thelatter representing an L-gamma-Glu or a D-gamma-Glu residue); wherein p′represents an integer in the range of 1 to 4; and D represents a drugsubstance; or X′ represents a linker of Formula Ie′:

wherein,

represents a covalent bond towards R¹′ or R²′; or X′ represents a linkerof Formula If′:

wherein,

represents a covalent bond towards R¹′ or R²′; or X′ represents a linkerof Formula Ig′:

wherein,

represents a covalent bond towards R¹′ or R²′; or X′ represents a linkerof Formula Ih′:

wherein,

represents a covalent bond towards R¹′ or R²′; or X′ represents a linkerof Formula Ii′:

wherein,

represents a covalent bond towards R¹′ or R²′; and W′ represents acovalent bond or a linker selected from the group consisting of—NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—, —NHCH₂CH₂CH₂(C═O)—, and—NHCH(COOH)CH₂CH₂(C═O)— (the latter representing an L-gamma-Glu or aD-gamma-Glu residue); and R¹′ and R²′, which may be identical ordifferent, each represents a group of Formula IIa′ or Formula IIb′:

wherein, one to four Y′ represents H; and none, one or two Y′ representsF, Cl, CF₂, CF₃, SF₅, OCF₃, SO₂CH₃ and/or SO₂CF₃; and one Y′ represents(a covalent bond representing) the attachment point to X′ of Formula I′;and when X′ is Formula Ie′, If′, Ig′ or Ih′, one Y in either R¹′ or R²′represents —(C═O)—W′—D, where W′ represents a covalent bond, or a linkerselected from the group consisting of —NHCH₂(C═O)—, —NHCH₂CH₂(C═O)—,—NHCH₂CH₂CH₂(C═O)—, and —NHCH(COOH)CH₂CH₂(C═O)— (the latter representingan L-gamma-Glu or a D-gamma-Glu residue); and wherein D represents adrug substance.
 15. (canceled)
 16. A diboron conjugate, wherein thediboron compound according to claim 11 is conjugated to a drug substancevia an optional linker.
 17. The diboron conjugate of claim 16, whereinthe diboron compound is conjugated to the drug substance via an optionallinker by derivatisation of the carboxylic acid moiety of the diboroncompound.